///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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//
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//
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// Filename: zipcpu.v
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// Filename: zipcpu.v
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//
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//
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// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
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// Project: Zip CPU -- a small, lightweight, RISC CPU soft core
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//
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//
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// Purpose: This is the top level module holding the core of the Zip CPU
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// Purpose: This is the top level module holding the core of the Zip CPU
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// together. The Zip CPU is designed to be as simple as possible.
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// together. The Zip CPU is designed to be as simple as possible.
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// The instruction set is about as RISC as you can get, there are
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// The instruction set is about as RISC as you can get, there are
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// only 16 instruction types supported (of which one isn't yet
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// only 16 instruction types supported (of which one isn't yet
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// supported ...) Please see the accompanying iset.html file
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// supported ...) Please see the accompanying iset.html file
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// for a description of these instructions.
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// for a description of these instructions.
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//
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//
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// All instructions are 32-bits wide. All bus accesses, both
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// All instructions are 32-bits wide. All bus accesses, both
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// address and data, are 32-bits over a wishbone bus.
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// address and data, are 32-bits over a wishbone bus.
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//
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//
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// The Zip CPU is fully pipelined with the following pipeline stages:
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// The Zip CPU is fully pipelined with the following pipeline stages:
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//
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//
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// 1. Prefetch, returns the instruction from memory. On the
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// 1. Prefetch, returns the instruction from memory. On the
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// Basys board that I'm working on, one instruction may be
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// Basys board that I'm working on, one instruction may be
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// issued every 20 clocks or so, unless and until I implement a
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// issued every 20 clocks or so, unless and until I implement a
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// cache or local memory.
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// cache or local memory.
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//
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//
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// 2. Instruction Decode
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// 2. Instruction Decode
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//
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//
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// 3. Read Operands
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// 3. Read Operands
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//
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//
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// 4. Apply Instruction
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// 4. Apply Instruction
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//
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//
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// 4. Write-back Results
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// 4. Write-back Results
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//
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//
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// A lot of difficult work has been placed into the pipeline stall
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// A lot of difficult work has been placed into the pipeline stall
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// handling. My original proposal was not to allow pipeline stalls at all.
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// handling. My original proposal was not to allow pipeline stalls at all.
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// The idea would be that the CPU would just run every clock and whatever
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// The idea would be that the CPU would just run every clock and whatever
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// stalled answer took place would just get fixed a clock or two later,
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// stalled answer took place would just get fixed a clock or two later,
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// meaning that the compiler could just schedule everything out.
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// meaning that the compiler could just schedule everything out.
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// This idea died at the memory interface, which can take a variable
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// This idea died at the memory interface, which can take a variable
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// amount of time to read or write any value, thus the whole CPU needed
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// amount of time to read or write any value, thus the whole CPU needed
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// to stall on a stalled memory access.
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// to stall on a stalled memory access.
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//
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//
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// My next idea was to just let things complete. I.e., once an instrution
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// My next idea was to just let things complete. I.e., once an instrution
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// starts, it continues to completion no matter what and we go on. This
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// starts, it continues to completion no matter what and we go on. This
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// failed at writing the PC. If the PC gets written in something such as
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// failed at writing the PC. If the PC gets written in something such as
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// a MOV PC,PC+5 instruction, 3 (or however long the pipeline is) clocks
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// a MOV PC,PC+5 instruction, 3 (or however long the pipeline is) clocks
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// later, if whether or not something happens in those clocks depends
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// later, if whether or not something happens in those clocks depends
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// upon the instruction fetch filling the pipeline, then the CPU has a
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// upon the instruction fetch filling the pipeline, then the CPU has a
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// non-deterministic behavior.
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// non-deterministic behavior.
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//
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//
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// This leads to two possibilities: either *everything* stalls upon a
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// This leads to two possibilities: either *everything* stalls upon a
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// stall condition, or partial results need to be destroyed before
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// stall condition, or partial results need to be destroyed before
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// they are written. This is made more difficult by the fact that
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// they are written. This is made more difficult by the fact that
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// once a command is written to the memory unit, whether it be a
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// once a command is written to the memory unit, whether it be a
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// read or a write, there is no undoing it--since peripherals on the
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// read or a write, there is no undoing it--since peripherals on the
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// bus may act upon the answer with whatever side effects they might
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// bus may act upon the answer with whatever side effects they might
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// have. (For example, writing a '1' to the interrupt register will
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// have. (For example, writing a '1' to the interrupt register will
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// clear certain interrupts ...) Further, since the memory ops depend
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// clear certain interrupts ...) Further, since the memory ops depend
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// upon conditions, the we'll need to wait for the condition codes to
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// upon conditions, the we'll need to wait for the condition codes to
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// be available before executing a memory op. Thus, memory ops can
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// be available before executing a memory op. Thus, memory ops can
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// proceed without stalling whenever either the previous instruction
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// proceed without stalling whenever either the previous instruction
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// doesn't write the flags register, or when the memory instruction doesn't
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// doesn't write the flags register, or when the memory instruction doesn't
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// depend upon the flags register.
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// depend upon the flags register.
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//
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//
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// The other possibility is that we leave independent instruction
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// The other possibility is that we leave independent instruction
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// execution behind, so that the pipeline is always full and stalls,
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// execution behind, so that the pipeline is always full and stalls,
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// or moves forward, together on every clock.
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// or moves forward, together on every clock.
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//
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//
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// For now, we pick the first approach: independent instruction execution.
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// For now, we pick the first approach: independent instruction execution.
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// Thus, if stage 2 stalls, stages 3-5 may still complete the instructions
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// Thus, if stage 2 stalls, stages 3-5 may still complete the instructions
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// in their pipeline. This leaves another problem: what happens on a
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// in their pipeline. This leaves another problem: what happens on a
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// MOV -1+PC,PC instruction? There will be four instructions behind this
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// MOV -1+PC,PC instruction? There will be four instructions behind this
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// one (or is it five?) that will need to be 'cancelled'. So here's
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// one (or is it five?) that will need to be 'cancelled'. So here's
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// the plan: Anything can be cancelled before the ALU/MEM stage,
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// the plan: Anything can be cancelled before the ALU/MEM stage,
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// since memory ops cannot be canceled after being issued. Thus, the
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// since memory ops cannot be canceled after being issued. Thus, the
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// ALU/MEM stage must stall if any prior instruction is going to write
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// ALU/MEM stage must stall if any prior instruction is going to write
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// the PC register (i.e. JMP).
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// the PC register (i.e. JMP).
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//
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//
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// Further, let's define a "STALL" as a reason to not execute a stage
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// Further, let's define a "STALL" as a reason to not execute a stage
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// due to some condition at or beyond the stage, and let's define
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// due to some condition at or beyond the stage, and let's define
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// a VALID flag to mean that this stage has completed. Thus, the clock
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// a VALID flag to mean that this stage has completed. Thus, the clock
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// enable for a stage is (STG[n-1]VALID)&&((~STG[n]VALID)||(~STG[n]STALL)).
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// enable for a stage is (STG[n-1]VALID)&&((~STG[n]VALID)||(~STG[n]STALL)).
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// The ALU/MEM stages will also depend upon a master clock enable
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// The ALU/MEM stages will also depend upon a master clock enable
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// (~SLEEP) condition as well.
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// (~SLEEP) condition as well.
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//
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//
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//
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//
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//
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//
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// Creator: Dan Gisselquist, Ph.D.
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// Creator: Dan Gisselquist, Ph.D.
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// Gisselquist Tecnology, LLC
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// Gisselquist Tecnology, LLC
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//
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//
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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//
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//
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// Copyright (C) 2015, Gisselquist Technology, LLC
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// Copyright (C) 2015, Gisselquist Technology, LLC
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//
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//
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// This program is free software (firmware): you can redistribute it and/or
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// This program is free software (firmware): you can redistribute it and/or
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// modify it under the terms of the GNU General Public License as published
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// modify it under the terms of the GNU General Public License as published
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// by the Free Software Foundation, either version 3 of the License, or (at
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// by the Free Software Foundation, either version 3 of the License, or (at
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// your option) any later version.
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// your option) any later version.
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//
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//
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// This program is distributed in the hope that it will be useful, but WITHOUT
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// ANY WARRANTY; without even the implied warranty of MERCHANTIBILITY or
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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// for more details.
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// for more details.
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//
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//
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// License: GPL, v3, as defined and found on www.gnu.org,
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// License: GPL, v3, as defined and found on www.gnu.org,
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// http://www.gnu.org/licenses/gpl.html
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// http://www.gnu.org/licenses/gpl.html
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//
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//
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//
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//
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///////////////////////////////////////////////////////////////////////////////
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///////////////////////////////////////////////////////////////////////////////
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//
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//
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`define CPU_CC_REG 4'he
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`define CPU_CC_REG 4'he
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`define CPU_PC_REG 4'hf
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`define CPU_PC_REG 4'hf
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`define CPU_TRAP_BIT 9
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`define CPU_TRAP_BIT 9
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`define CPU_BREAK_BIT 7
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`define CPU_BREAK_BIT 7
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`define CPU_STEP_BIT 6
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`define CPU_STEP_BIT 6
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`define CPU_GIE_BIT 5
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`define CPU_GIE_BIT 5
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`define CPU_SLEEP_BIT 4
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`define CPU_SLEEP_BIT 4
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module zipcpu(i_clk, i_rst, i_interrupt,
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module zipcpu(i_clk, i_rst, i_interrupt,
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// Debug interface
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// Debug interface
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i_halt, i_clear_pf_cache, i_dbg_reg, i_dbg_we, i_dbg_data,
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i_halt, i_clear_pf_cache, i_dbg_reg, i_dbg_we, i_dbg_data,
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o_dbg_stall, o_dbg_reg, o_dbg_cc,
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o_dbg_stall, o_dbg_reg, o_dbg_cc,
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o_break,
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o_break,
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// CPU interface to the wishbone bus
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// CPU interface to the wishbone bus
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o_wb_cyc, o_wb_stb, o_wb_we, o_wb_addr, o_wb_data,
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o_wb_cyc, o_wb_stb, o_wb_we, o_wb_addr, o_wb_data,
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i_wb_ack, i_wb_stall, i_wb_data,
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i_wb_ack, i_wb_stall, i_wb_data,
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// Accounting/CPU usage interface
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// Accounting/CPU usage interface
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o_op_stall, o_pf_stall, o_i_count);
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o_op_stall, o_pf_stall, o_i_count);
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parameter RESET_ADDRESS=32'h0100000;
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parameter RESET_ADDRESS=32'h0100000;
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input i_clk, i_rst, i_interrupt;
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input i_clk, i_rst, i_interrupt;
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// Debug interface -- inputs
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// Debug interface -- inputs
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input i_halt, i_clear_pf_cache;
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input i_halt, i_clear_pf_cache;
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input [4:0] i_dbg_reg;
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input [4:0] i_dbg_reg;
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input i_dbg_we;
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input i_dbg_we;
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input [31:0] i_dbg_data;
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input [31:0] i_dbg_data;
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// Debug interface -- outputs
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// Debug interface -- outputs
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output reg o_dbg_stall;
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output reg o_dbg_stall;
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output reg [31:0] o_dbg_reg;
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output reg [31:0] o_dbg_reg;
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output reg [1:0] o_dbg_cc;
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output reg [1:0] o_dbg_cc;
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output wire o_break;
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output wire o_break;
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// Wishbone interface -- outputs
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// Wishbone interface -- outputs
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output wire o_wb_cyc, o_wb_stb, o_wb_we;
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output wire o_wb_cyc, o_wb_stb, o_wb_we;
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output wire [31:0] o_wb_addr, o_wb_data;
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output wire [31:0] o_wb_addr, o_wb_data;
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// Wishbone interface -- inputs
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// Wishbone interface -- inputs
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input i_wb_ack, i_wb_stall;
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input i_wb_ack, i_wb_stall;
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input [31:0] i_wb_data;
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input [31:0] i_wb_data;
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// Accounting outputs ... to help us count stalls and usage
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// Accounting outputs ... to help us count stalls and usage
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output wire o_op_stall;
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output wire o_op_stall;
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output wire o_pf_stall;
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output wire o_pf_stall;
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output wire o_i_count;
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output wire o_i_count;
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// Registers
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// Registers
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reg [31:0] regset [0:31];
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reg [31:0] regset [0:31];
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// Condition codes
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// Condition codes
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reg [3:0] flags, iflags; // (TRAP,FPEN,BREAKEN,STEP,GIE,SLEEP ), V, N, C, Z
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reg [3:0] flags, iflags; // (TRAP,FPEN,BREAKEN,STEP,GIE,SLEEP ), V, N, C, Z
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wire [9:0] w_uflags, w_iflags;
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wire [9:0] w_uflags, w_iflags;
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reg trap, break_en, step, gie, sleep;
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reg trap, break_en, step, gie, sleep;
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// The master chip enable
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// The master chip enable
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wire master_ce;
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wire master_ce;
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//
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//
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//
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//
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// PIPELINE STAGE #1 :: Prefetch
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// PIPELINE STAGE #1 :: Prefetch
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// Variable declarations
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// Variable declarations
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//
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//
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reg [31:0] pf_pc;
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reg [31:0] pf_pc;
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reg new_pc, op_break;
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reg new_pc, op_break;
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wire clear_pipeline;
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wire clear_pipeline;
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assign clear_pipeline = new_pc || i_clear_pf_cache || op_break;
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assign clear_pipeline = new_pc || i_clear_pf_cache || op_break;
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wire dcd_stalled;
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wire dcd_stalled;
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wire pf_cyc, pf_stb, pf_we, pf_busy, pf_ack, pf_stall;
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wire pf_cyc, pf_stb, pf_we, pf_busy, pf_ack, pf_stall;
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wire [31:0] pf_addr, pf_data;
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wire [31:0] pf_addr, pf_data;
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wire [31:0] instruction, instruction_pc;
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wire [31:0] instruction, instruction_pc;
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wire pf_valid, instruction_gie;
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wire pf_valid, instruction_gie;
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//
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//
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//
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//
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// PIPELINE STAGE #2 :: Instruction Decode
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// PIPELINE STAGE #2 :: Instruction Decode
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// Variable declarations
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// Variable declarations
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//
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//
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//
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//
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reg opvalid, opvalid_mem, opvalid_alu, op_wr_pc;
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reg opvalid, opvalid_mem, opvalid_alu, op_wr_pc;
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wire op_stall, dcd_ce;
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wire op_stall, dcd_ce;
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reg [3:0] dcdOp;
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reg [3:0] dcdOp;
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reg [4:0] dcdA, dcdB;
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reg [4:0] dcdA, dcdB;
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reg dcdA_cc, dcdB_cc, dcdA_pc, dcdB_pc;
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reg dcdA_cc, dcdB_cc, dcdA_pc, dcdB_pc;
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reg [3:0] dcdF;
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reg [3:0] dcdF;
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reg dcdA_rd, dcdA_wr, dcdB_rd, dcdvalid,
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reg dcdA_rd, dcdA_wr, dcdB_rd, dcdvalid,
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dcdM, dcdF_wr, dcd_gie, dcd_break;
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dcdM, dcdF_wr, dcd_gie, dcd_break;
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reg [31:0] dcd_pc;
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reg [31:0] dcd_pc;
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reg [23:0] r_dcdI;
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reg [23:0] r_dcdI;
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wire dcdA_stall, dcdB_stall, dcdF_stall;
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wire dcdA_stall, dcdB_stall, dcdF_stall;
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//
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//
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//
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//
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// PIPELINE STAGE #3 :: Read Operands
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// PIPELINE STAGE #3 :: Read Operands
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// Variable declarations
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// Variable declarations
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//
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//
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//
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//
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//
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//
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// Now, let's read our operands
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// Now, let's read our operands
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reg [4:0] alu_reg;
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reg [4:0] alu_reg;
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reg [3:0] opn;
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reg [3:0] opn;
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reg [4:0] opR;
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reg [4:0] opR;
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reg [31:0] r_opA, r_opB, op_pc;
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reg [31:0] r_opA, r_opB, op_pc;
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wire [31:0] w_opA, w_opB;
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wire [31:0] w_opA, w_opB;
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wire [31:0] opA_nowait, opB_nowait, opA, opB;
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wire [31:0] opA_nowait, opB_nowait, opA, opB;
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reg opR_wr, opR_cc, opF_wr, op_gie,
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reg opR_wr, opR_cc, opF_wr, op_gie,
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opA_rd, opB_rd;
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opA_rd, opB_rd;
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wire [9:0] opFl;
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wire [9:0] opFl;
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reg [6:0] r_opF;
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reg [6:0] r_opF;
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wire [8:0] opF;
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wire [8:0] opF;
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wire op_ce;
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wire op_ce;
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//
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//
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//
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//
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// PIPELINE STAGE #4 :: ALU / Memory
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// PIPELINE STAGE #4 :: ALU / Memory
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// Variable declarations
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// Variable declarations
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//
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//
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//
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//
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reg [31:0] alu_pc;
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reg [31:0] alu_pc;
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reg alu_pc_valid;;
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reg alu_pc_valid;;
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wire alu_ce, alu_stall;
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wire alu_ce, alu_stall;
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wire [31:0] alu_result;
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wire [31:0] alu_result;
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wire [3:0] alu_flags;
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wire [3:0] alu_flags;
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wire alu_valid;
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wire alu_valid;
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wire set_cond;
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wire set_cond;
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reg alu_wr, alF_wr, alu_gie;
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reg alu_wr, alF_wr, alu_gie;
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wire mem_ce, mem_stalled;
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wire mem_ce, mem_stalled;
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wire mem_valid, mem_ack, mem_stall,
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wire mem_valid, mem_ack, mem_stall,
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mem_cyc, mem_stb, mem_we;
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mem_cyc, mem_stb, mem_we;
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wire [4:0] mem_wreg;
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wire [4:0] mem_wreg;
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wire mem_busy, mem_rdbusy;
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wire mem_busy, mem_rdbusy;
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wire [31:0] mem_addr, mem_data, mem_result;
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wire [31:0] mem_addr, mem_data, mem_result;
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//
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//
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//
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//
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// PIPELINE STAGE #5 :: Write-back
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// PIPELINE STAGE #5 :: Write-back
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// Variable declarations
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// Variable declarations
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//
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//
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wire wr_reg_ce, wr_flags_ce, wr_write_pc, wr_write_cc;
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wire wr_reg_ce, wr_flags_ce, wr_write_pc, wr_write_cc;
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wire [4:0] wr_reg_id;
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wire [4:0] wr_reg_id;
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wire [31:0] wr_reg_vl;
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wire [31:0] wr_reg_vl;
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wire w_switch_to_interrupt, w_release_from_interrupt;
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wire w_switch_to_interrupt, w_release_from_interrupt;
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reg [31:0] upc, ipc;
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reg [31:0] upc, ipc;
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//
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//
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// MASTER: clock enable.
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// MASTER: clock enable.
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//
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//
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assign master_ce = (~i_halt)&&(~o_break)&&(~sleep)&&(~mem_rdbusy);
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assign master_ce = (~i_halt)&&(~o_break)&&(~sleep)&&(~mem_rdbusy);
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//
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//
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// PIPELINE STAGE #1 :: Prefetch
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// PIPELINE STAGE #1 :: Prefetch
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// Calculate stall conditions
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// Calculate stall conditions
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//
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//
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// PIPELINE STAGE #2 :: Instruction Decode
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// PIPELINE STAGE #2 :: Instruction Decode
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// Calculate stall conditions
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// Calculate stall conditions
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assign dcd_ce = (pf_valid)&&(~dcd_stalled);
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assign dcd_ce = (pf_valid)&&(~dcd_stalled);
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assign dcd_stalled = (dcdvalid)&&(
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assign dcd_stalled = (dcdvalid)&&(
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(op_stall)
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(op_stall)
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||((dcdA_stall)||(dcdB_stall)||(dcdF_stall))
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||((dcdA_stall)||(dcdB_stall)||(dcdF_stall))
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||((opvalid)&&((op_wr_pc)||(opR_cc))));
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||((opvalid)&&((op_wr_pc)||(opR_cc))));
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//
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//
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// PIPELINE STAGE #3 :: Read Operands
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// PIPELINE STAGE #3 :: Read Operands
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// Calculate stall conditions
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// Calculate stall conditions
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assign op_stall = ((mem_stalled)&&(opvalid_mem))
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assign op_stall = ((mem_stalled)&&(opvalid_mem))
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||((alu_stall)&&(opvalid_alu));
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||((alu_stall)&&(opvalid_alu));
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assign op_ce = (dcdvalid)&&((~opvalid)||(~op_stall));
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assign op_ce = (dcdvalid)&&((~opvalid)||(~op_stall));
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//
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//
|
// PIPELINE STAGE #4 :: ALU / Memory
|
// PIPELINE STAGE #4 :: ALU / Memory
|
// Calculate stall conditions
|
// Calculate stall conditions
|
assign alu_stall = (((~master_ce)||(mem_rdbusy))&&(opvalid_alu))
|
assign alu_stall = (((~master_ce)||(mem_rdbusy))&&(opvalid_alu))
|
||((opvalid)&&(wr_reg_ce)&&(wr_reg_id[4] == op_gie)
|
||((opvalid)&&(wr_reg_ce)&&(wr_reg_id[4] == op_gie)
|
&&(wr_write_pc)||(wr_write_cc));
|
&&(wr_write_pc)||(wr_write_cc));
|
assign alu_ce = (master_ce)&&(opvalid_alu)&&(~alu_stall)&&(~clear_pipeline);
|
assign alu_ce = (master_ce)&&(opvalid_alu)&&(~alu_stall)&&(~clear_pipeline);
|
//
|
//
|
assign mem_ce = (master_ce)&&(opvalid_mem)&&(~mem_stalled)&&(~clear_pipeline)&&(set_cond);
|
assign mem_ce = (master_ce)&&(opvalid_mem)&&(~mem_stalled)&&(~clear_pipeline)&&(set_cond);
|
assign mem_stalled = (mem_busy)||((opvalid_mem)&&(
|
assign mem_stalled = (mem_busy)||((opvalid_mem)&&(
|
(~master_ce)
|
(~master_ce)
|
// Stall waiting for flags to be valid
|
// Stall waiting for flags to be valid
|
||((~opF[8])&&(
|
|
((wr_reg_ce)&&(wr_reg_id[4:0] == {op_gie,`CPU_CC_REG}))
|
|
// Do I need this last condition?
|
|
||(wr_flags_ce)))
|
|
// Or waiting for a write to the PC register
|
// Or waiting for a write to the PC register
|
// Or CC register, since that can change the
|
// Or CC register, since that can change the
|
// PC as well
|
// PC as well
|
||((wr_reg_ce)&&(wr_reg_id[4] == op_gie)&&((wr_write_pc)||(wr_write_cc)))));
|
||((wr_reg_ce)&&(wr_reg_id[4] == op_gie)&&((wr_write_pc)||(wr_write_cc)))));
|
|
|
|
|
//
|
//
|
//
|
//
|
// PIPELINE STAGE #1 :: Prefetch
|
// PIPELINE STAGE #1 :: Prefetch
|
//
|
//
|
//
|
//
|
`ifdef SINGLE_FETCH
|
`ifdef SINGLE_FETCH
|
wire pf_ce;
|
wire pf_ce;
|
|
|
assign pf_ce = (~dcd_stalled);
|
assign pf_ce = (~dcd_stalled);
|
prefetch pf(i_clk, i_rst, (pf_ce), pf_pc, gie,
|
prefetch pf(i_clk, i_rst, (pf_ce), pf_pc, gie,
|
instruction, instruction_pc, instruction_gie,
|
instruction, instruction_pc, instruction_gie,
|
pf_valid,
|
pf_valid,
|
pf_cyc, pf_stb, pf_we, pf_addr,
|
pf_cyc, pf_stb, pf_we, pf_addr,
|
pf_data,
|
pf_data,
|
pf_ack, pf_stall, i_wb_data);
|
pf_ack, pf_stall, i_wb_data);
|
`else // Pipe fetch
|
`else // Pipe fetch
|
pipefetch #(RESET_ADDRESS)
|
pipefetch #(RESET_ADDRESS)
|
pf(i_clk, i_rst, new_pc, i_clear_pf_cache, ~dcd_stalled, pf_pc,
|
pf(i_clk, i_rst, new_pc, i_clear_pf_cache, ~dcd_stalled, pf_pc,
|
instruction, instruction_pc, pf_valid,
|
instruction, instruction_pc, pf_valid,
|
pf_cyc, pf_stb, pf_we, pf_addr, pf_data,
|
pf_cyc, pf_stb, pf_we, pf_addr, pf_data,
|
pf_ack, pf_stall, i_wb_data,
|
pf_ack, pf_stall, i_wb_data,
|
mem_cyc);
|
mem_cyc);
|
assign instruction_gie = gie;
|
assign instruction_gie = gie;
|
`endif
|
`endif
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
dcdvalid <= 1'b0;
|
dcdvalid <= 1'b0;
|
else if (dcd_ce)
|
else if (dcd_ce)
|
dcdvalid <= (~clear_pipeline);
|
dcdvalid <= (~clear_pipeline);
|
else if ((~dcd_stalled)||(clear_pipeline))
|
else if ((~dcd_stalled)||(clear_pipeline))
|
dcdvalid <= 1'b0;
|
dcdvalid <= 1'b0;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (dcd_ce)
|
if (dcd_ce)
|
begin
|
begin
|
dcd_pc <= instruction_pc+1;
|
dcd_pc <= instruction_pc+1;
|
|
|
// Record what operation we are doing
|
// Record what operation we are doing
|
dcdOp <= instruction[31:28];
|
dcdOp <= instruction[31:28];
|
|
|
// Default values
|
// Default values
|
dcdA[4:0] <= { instruction_gie, instruction[27:24] };
|
dcdA[4:0] <= { instruction_gie, instruction[27:24] };
|
dcdB[4:0] <= { instruction_gie, instruction[19:16] };
|
dcdB[4:0] <= { instruction_gie, instruction[19:16] };
|
dcdA_cc <= (instruction[27:24] == `CPU_CC_REG);
|
dcdA_cc <= (instruction[27:24] == `CPU_CC_REG);
|
dcdB_cc <= (instruction[19:16] == `CPU_CC_REG);
|
dcdB_cc <= (instruction[19:16] == `CPU_CC_REG);
|
dcdA_pc <= (instruction[27:24] == `CPU_PC_REG);
|
dcdA_pc <= (instruction[27:24] == `CPU_PC_REG);
|
dcdB_pc <= (instruction[19:16] == `CPU_PC_REG);
|
dcdB_pc <= (instruction[19:16] == `CPU_PC_REG);
|
dcdM <= 1'b0;
|
dcdM <= 1'b0;
|
dcdF_wr <= 1'b1;
|
dcdF_wr <= 1'b1;
|
|
|
// Set the condition under which we do this operation
|
// Set the condition under which we do this operation
|
// The top four bits are a mask, the bottom four the
|
// The top four bits are a mask, the bottom four the
|
// value the flags must equal once anded with the mask
|
// value the flags must equal once anded with the mask
|
dcdF <= { (instruction[23:21]==3'h0), instruction[23:21] };
|
dcdF <= { (instruction[23:21]==3'h0), instruction[23:21] };
|
casez(instruction[31:28])
|
casez(instruction[31:28])
|
4'h2: begin // Move instruction
|
4'h2: begin // Move instruction
|
if (~instruction_gie)
|
if (~instruction_gie)
|
begin
|
begin
|
dcdA[4] <= instruction[20];
|
dcdA[4] <= instruction[20];
|
dcdB[4] <= instruction[15];
|
dcdB[4] <= instruction[15];
|
end
|
end
|
dcdA_wr <= 1'b1;
|
dcdA_wr <= 1'b1;
|
dcdA_rd <= 1'b0;
|
dcdA_rd <= 1'b0;
|
dcdB_rd <= 1'b1;
|
dcdB_rd <= 1'b1;
|
r_dcdI <= { {(9){instruction[14]}}, instruction[14:0] };
|
r_dcdI <= { {(9){instruction[14]}}, instruction[14:0] };
|
dcdF_wr <= 1'b0; // Don't write flags
|
dcdF_wr <= 1'b0; // Don't write flags
|
end
|
end
|
4'h3: begin // Load immediate
|
4'h3: begin // Load immediate
|
dcdA_wr <= 1'b1;
|
dcdA_wr <= 1'b1;
|
dcdA_rd <= 1'b0;
|
dcdA_rd <= 1'b0;
|
dcdB_rd <= 1'b0;
|
dcdB_rd <= 1'b0;
|
r_dcdI <= { instruction[23:0] };
|
r_dcdI <= { instruction[23:0] };
|
dcdF_wr <= 1'b0; // Don't write flags
|
dcdF_wr <= 1'b0; // Don't write flags
|
dcdF <= 4'h8; // This is unconditional
|
dcdF <= 4'h8; // This is unconditional
|
dcdOp <= 4'h2;
|
dcdOp <= 4'h2;
|
end
|
end
|
4'h4: begin // Multiply, LDI[HI|LO], or NOOP/BREAK
|
4'h4: begin // Multiply, LDI[HI|LO], or NOOP/BREAK
|
// Don't write flags except for multiplies
|
// Don't write flags except for multiplies
|
dcdF_wr <= (instruction[27:25] != 3'h7);
|
dcdF_wr <= (instruction[27:25] != 3'h7);
|
r_dcdI <= { 8'h00, instruction[15:0] };
|
r_dcdI <= { 8'h00, instruction[15:0] };
|
if (instruction[27:24] == 4'he)
|
if (instruction[27:24] == 4'he)
|
begin
|
begin
|
// NOOP instruction
|
// NOOP instruction
|
dcdA_wr <= 1'b0;
|
dcdA_wr <= 1'b0;
|
dcdA_rd <= 1'b0;
|
dcdA_rd <= 1'b0;
|
dcdB_rd <= 1'b0;
|
dcdB_rd <= 1'b0;
|
dcdOp <= 4'h2;
|
dcdOp <= 4'h2;
|
end else if (instruction[27:24] == 4'hf)
|
end else if (instruction[27:24] == 4'hf)
|
begin // Load partial immediate(s)
|
begin // Load partial immediate(s)
|
dcdA_wr <= 1'b1;
|
dcdA_wr <= 1'b1;
|
dcdA_rd <= 1'b1;
|
dcdA_rd <= 1'b1;
|
dcdB_rd <= 1'b0;
|
dcdB_rd <= 1'b0;
|
dcdA[4:0] <= { instruction_gie, instruction[19:16] };
|
dcdA[4:0] <= { instruction_gie, instruction[19:16] };
|
dcdA_cc <= (instruction[19:16] == `CPU_CC_REG);
|
dcdA_cc <= (instruction[19:16] == `CPU_CC_REG);
|
dcdA_pc <= (instruction[19:16] == `CPU_PC_REG);
|
dcdA_pc <= (instruction[19:16] == `CPU_PC_REG);
|
dcdOp <= { 3'h3, instruction[20] };
|
dcdOp <= { 3'h3, instruction[20] };
|
end else begin
|
end else begin
|
// Actual multiply instruction
|
// Actual multiply instruction
|
r_dcdI <= { 8'h00, instruction[15:0] };
|
r_dcdI <= { 8'h00, instruction[15:0] };
|
dcdA_rd <= 1'b1;
|
dcdA_rd <= 1'b1;
|
dcdB_rd <= (instruction[19:16] != 4'hf);
|
dcdB_rd <= (instruction[19:16] != 4'hf);
|
dcdOp[3:0] <= (instruction[20])? 4'h4:4'h3;
|
dcdOp[3:0] <= (instruction[20])? 4'h4:4'h3;
|
end end
|
end end
|
4'b011?: begin // Load/Store
|
4'b011?: begin // Load/Store
|
dcdF_wr <= 1'b0; // Don't write flags
|
dcdF_wr <= 1'b0; // Don't write flags
|
dcdA_wr <= (~instruction[28]); // Write on loads
|
dcdA_wr <= (~instruction[28]); // Write on loads
|
dcdA_rd <= (instruction[28]); // Read on stores
|
dcdA_rd <= (instruction[28]); // Read on stores
|
dcdB_rd <= instruction[20];
|
dcdB_rd <= instruction[20];
|
if (instruction[20])
|
if (instruction[20])
|
r_dcdI <= { {(8){instruction[15]}}, instruction[15:0] };
|
r_dcdI <= { {(8){instruction[15]}}, instruction[15:0] };
|
else
|
else
|
r_dcdI <= { {(4){instruction[19]}}, instruction[19:0] };
|
r_dcdI <= { {(4){instruction[19]}}, instruction[19:0] };
|
dcdM <= 1'b1; // Memory operation
|
dcdM <= 1'b1; // Memory operation
|
end
|
end
|
default: begin
|
default: begin
|
dcdA_wr <= (instruction[31])||(instruction[31:28]==4'h5);
|
dcdA_wr <= (instruction[31])||(instruction[31:28]==4'h5);
|
dcdA_rd <= 1'b1;
|
dcdA_rd <= 1'b1;
|
dcdB_rd <= instruction[20];
|
dcdB_rd <= instruction[20];
|
if (instruction[20])
|
if (instruction[20])
|
r_dcdI <= { {(8){instruction[15]}}, instruction[15:0] };
|
r_dcdI <= { {(8){instruction[15]}}, instruction[15:0] };
|
else
|
else
|
r_dcdI <= { {(4){instruction[19]}}, instruction[19:0] };
|
r_dcdI <= { {(4){instruction[19]}}, instruction[19:0] };
|
end
|
end
|
endcase
|
endcase
|
|
|
|
|
dcd_gie <= instruction_gie;
|
dcd_gie <= instruction_gie;
|
end
|
end
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (dcd_ce)
|
if (dcd_ce)
|
dcd_break <= (instruction[31:0] == 32'h4e000001);
|
dcd_break <= (instruction[31:0] == 32'h4e000001);
|
else
|
else
|
dcd_break <= 1'b0;
|
dcd_break <= 1'b0;
|
|
|
|
|
//
|
//
|
//
|
//
|
// PIPELINE STAGE #3 :: Read Operands (Registers)
|
// PIPELINE STAGE #3 :: Read Operands (Registers)
|
//
|
//
|
//
|
//
|
assign w_opA = regset[dcdA];
|
assign w_opA = regset[dcdA];
|
assign w_opB = regset[dcdB];
|
assign w_opB = regset[dcdB];
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce) // &&(dcdvalid))
|
if (op_ce) // &&(dcdvalid))
|
begin
|
begin
|
if ((wr_reg_ce)&&(wr_reg_id == dcdA))
|
if ((wr_reg_ce)&&(wr_reg_id == dcdA))
|
r_opA <= wr_reg_vl;
|
r_opA <= wr_reg_vl;
|
else if ((dcdA_pc)&&(dcdA[4] == dcd_gie))
|
else if ((dcdA_pc)&&(dcdA[4] == dcd_gie))
|
r_opA <= dcd_pc;
|
r_opA <= dcd_pc;
|
else if (dcdA_pc)
|
else if (dcdA_pc)
|
r_opA <= upc;
|
r_opA <= upc;
|
else if (dcdA_cc)
|
else if (dcdA_cc)
|
r_opA <= { w_opA[31:10], (dcd_gie)?w_uflags:w_iflags };
|
r_opA <= { w_opA[31:10], (dcd_gie)?w_uflags:w_iflags };
|
else
|
else
|
r_opA <= w_opA;
|
r_opA <= w_opA;
|
end
|
end
|
wire [31:0] dcdI;
|
wire [31:0] dcdI;
|
assign dcdI = { {(8){r_dcdI[23]}}, r_dcdI };
|
assign dcdI = { {(8){r_dcdI[23]}}, r_dcdI };
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce) // &&(dcdvalid))
|
if (op_ce) // &&(dcdvalid))
|
begin
|
begin
|
if (~dcdB_rd)
|
if (~dcdB_rd)
|
r_opB <= dcdI;
|
r_opB <= dcdI;
|
else if ((wr_reg_ce)&&(wr_reg_id == dcdB))
|
else if ((wr_reg_ce)&&(wr_reg_id == dcdB))
|
r_opB <= wr_reg_vl + dcdI;
|
r_opB <= wr_reg_vl + dcdI;
|
else if ((dcdB_pc)&&(dcdB[4] == dcd_gie))
|
else if ((dcdB_pc)&&(dcdB[4] == dcd_gie))
|
r_opB <= dcd_pc + dcdI;
|
r_opB <= dcd_pc + dcdI;
|
else if (dcdB_pc) // & dcdB[4] != dcd_gie thus is user
|
else if (dcdB_pc) // & dcdB[4] != dcd_gie thus is user
|
r_opB <= upc + dcdI;
|
r_opB <= upc + dcdI;
|
else if (dcdB_cc)
|
else if (dcdB_cc)
|
r_opB <= { w_opB[31:10], (dcd_gie)?w_uflags:w_iflags} + dcdI;
|
r_opB <= { w_opB[31:10], (dcd_gie)?w_uflags:w_iflags} + dcdI;
|
else
|
else
|
r_opB <= regset[dcdB] + dcdI;
|
r_opB <= regset[dcdB] + dcdI;
|
end
|
end
|
|
|
// The logic here has become more complex than it should be, no thanks
|
// The logic here has become more complex than it should be, no thanks
|
// to Xilinx's Vivado trying to help. The conditions are supposed to
|
// to Xilinx's Vivado trying to help. The conditions are supposed to
|
// be two sets of four bits: the top bits specify what bits matter, the
|
// be two sets of four bits: the top bits specify what bits matter, the
|
// bottom specify what those top bits must equal. However, two of
|
// bottom specify what those top bits must equal. However, two of
|
// conditions check whether bits are on, and those are the only two
|
// conditions check whether bits are on, and those are the only two
|
// conditions checking those bits. Therefore, Vivado complains that
|
// conditions checking those bits. Therefore, Vivado complains that
|
// these two bits are redundant. Hence the convoluted expression
|
// these two bits are redundant. Hence the convoluted expression
|
// below, arriving at what we finally want in the (now wire net)
|
// below, arriving at what we finally want in the (now wire net)
|
// opF.
|
// opF.
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce)
|
if (op_ce)
|
begin // Set the flag condition codes
|
begin // Set the flag condition codes
|
case(dcdF[2:0])
|
case(dcdF[2:0])
|
3'h0: r_opF <= 7'h80; // Always
|
3'h0: r_opF <= 7'h80; // Always
|
3'h1: r_opF <= 7'h11; // Z
|
3'h1: r_opF <= 7'h11; // Z
|
3'h2: r_opF <= 7'h10; // NE
|
3'h2: r_opF <= 7'h10; // NE
|
3'h3: r_opF <= 7'h20; // GE (!N)
|
3'h3: r_opF <= 7'h20; // GE (!N)
|
3'h4: r_opF <= 7'h30; // GT (!N&!Z)
|
3'h4: r_opF <= 7'h30; // GT (!N&!Z)
|
3'h5: r_opF <= 7'h24; // LT
|
3'h5: r_opF <= 7'h24; // LT
|
3'h6: r_opF <= 7'h02; // C
|
3'h6: r_opF <= 7'h02; // C
|
3'h7: r_opF <= 7'h08; // V
|
3'h7: r_opF <= 7'h08; // V
|
endcase
|
endcase
|
end
|
end
|
assign opF = { r_opF[6], r_opF[3], r_opF[5], r_opF[1], r_opF[4:0] };
|
assign opF = { r_opF[6], r_opF[3], r_opF[5], r_opF[1], r_opF[4:0] };
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
begin
|
begin
|
opvalid <= 1'b0;
|
opvalid <= 1'b0;
|
opvalid_alu <= 1'b0;
|
opvalid_alu <= 1'b0;
|
opvalid_mem <= 1'b0;
|
opvalid_mem <= 1'b0;
|
end else if (op_ce)
|
end else if (op_ce)
|
begin
|
begin
|
// Do we have a valid instruction?
|
// Do we have a valid instruction?
|
// The decoder may vote to stall one of its
|
// The decoder may vote to stall one of its
|
// instructions based upon something we currently
|
// instructions based upon something we currently
|
// have in our queue. This instruction must then
|
// have in our queue. This instruction must then
|
// move forward, and get a stall cycle inserted.
|
// move forward, and get a stall cycle inserted.
|
// Hence, the test on dcd_stalled here. If we must
|
// Hence, the test on dcd_stalled here. If we must
|
// wait until our operands are valid, then we aren't
|
// wait until our operands are valid, then we aren't
|
// valid yet until then.
|
// valid yet until then.
|
opvalid<= (~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
opvalid<= (~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
opvalid_alu <= (~dcdM)&&(~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
opvalid_alu <= (~dcdM)&&(~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
opvalid_mem <= (dcdM)&&(~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
opvalid_mem <= (dcdM)&&(~clear_pipeline)&&(dcdvalid)&&(~dcd_stalled);
|
end else if ((~op_stall)||(clear_pipeline))
|
end else if ((~op_stall)||(clear_pipeline))
|
begin
|
begin
|
opvalid <= 1'b0;
|
opvalid <= 1'b0;
|
opvalid_alu <= 1'b0;
|
opvalid_alu <= 1'b0;
|
opvalid_mem <= 1'b0;
|
opvalid_mem <= 1'b0;
|
end
|
end
|
|
|
// Here's part of our debug interface. When we recognize a break
|
// Here's part of our debug interface. When we recognize a break
|
// instruction, we set the op_break flag. That'll prevent this
|
// instruction, we set the op_break flag. That'll prevent this
|
// instruction from entering the ALU, and cause an interrupt before
|
// instruction from entering the ALU, and cause an interrupt before
|
// this instruction. Thus, returning to this code will cause the
|
// this instruction. Thus, returning to this code will cause the
|
// break to repeat and continue upon return. To get out of this
|
// break to repeat and continue upon return. To get out of this
|
// condition, replace the break instruction with what it is supposed
|
// condition, replace the break instruction with what it is supposed
|
// to be, step through it, and then replace it back. In this fashion,
|
// to be, step through it, and then replace it back. In this fashion,
|
// a debugger can step through code.
|
// a debugger can step through code.
|
// assign w_op_break = (dcd_break)&&(r_dcdI[15:0] == 16'h0001);
|
// assign w_op_break = (dcd_break)&&(r_dcdI[15:0] == 16'h0001);
|
initial op_break = 1'b0;
|
initial op_break = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst) op_break <= 1'b0;
|
if (i_rst) op_break <= 1'b0;
|
else if (op_ce) op_break <= (dcd_break);
|
else if (op_ce) op_break <= (dcd_break);
|
else if ((clear_pipeline)||(~opvalid))
|
else if ((clear_pipeline)||(~opvalid))
|
op_break <= 1'b0;
|
op_break <= 1'b0;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce)
|
if (op_ce)
|
begin
|
begin
|
opn <= dcdOp; // Which ALU operation?
|
opn <= dcdOp; // Which ALU operation?
|
// opM <= dcdM; // Is this a memory operation?
|
// opM <= dcdM; // Is this a memory operation?
|
// Will we write the flags/CC Register with our result?
|
// Will we write the flags/CC Register with our result?
|
opF_wr <= (dcdF_wr)&&((~dcdA_cc)||(~dcdA_wr));
|
opF_wr <= (dcdF_wr)&&((~dcdA_cc)||(~dcdA_wr));
|
// Will we be writing our results into a register?
|
// Will we be writing our results into a register?
|
opR_wr <= dcdA_wr;
|
opR_wr <= dcdA_wr;
|
// What register will these results be written into?
|
// What register will these results be written into?
|
opR <= dcdA;
|
opR <= dcdA;
|
opR_cc <= (dcdA_wr)&&(dcdA_cc);
|
opR_cc <= (dcdA_wr)&&(dcdA_cc);
|
// User level (1), vs supervisor (0)/interrupts disabled
|
// User level (1), vs supervisor (0)/interrupts disabled
|
op_gie <= dcd_gie;
|
op_gie <= dcd_gie;
|
|
|
// We're not done with these yet--we still need them
|
// We're not done with these yet--we still need them
|
// for the unclocked assign. We need the unclocked
|
// for the unclocked assign. We need the unclocked
|
// assign so that there's no wait state between an
|
// assign so that there's no wait state between an
|
// ALU or memory result and the next register that may
|
// ALU or memory result and the next register that may
|
// use that value.
|
// use that value.
|
opA_rd <= dcdA_rd;
|
opA_rd <= dcdA_rd;
|
opB_rd <= dcdB_rd;
|
opB_rd <= dcdB_rd;
|
op_pc <= dcd_pc;
|
op_pc <= dcd_pc;
|
//
|
//
|
op_wr_pc <= ((dcdA_wr)&&(dcdA_pc));
|
op_wr_pc <= ((dcdA_wr)&&(dcdA_pc)&&(dcdA[4] == dcd_gie));
|
end
|
end
|
assign opFl = (op_gie)?(w_uflags):(w_iflags);
|
assign opFl = (op_gie)?(w_uflags):(w_iflags);
|
|
|
// This is tricky. First, the PC and Flags registers aren't kept in
|
// This is tricky. First, the PC and Flags registers aren't kept in
|
// register set but in special registers of their own. So step one
|
// register set but in special registers of their own. So step one
|
// is to select the right register. Step to is to replace that
|
// is to select the right register. Step to is to replace that
|
// register with the results of an ALU or memory operation, if such
|
// register with the results of an ALU or memory operation, if such
|
// results are now available. Otherwise, we'd need to insert a wait
|
// results are now available. Otherwise, we'd need to insert a wait
|
// state of some type.
|
// state of some type.
|
//
|
//
|
// The alternative approach would be to define some sort of
|
// The alternative approach would be to define some sort of
|
// op_stall wire, which would stall any upstream stage.
|
// op_stall wire, which would stall any upstream stage.
|
// We'll create a flag here to start our coordination. Once we
|
// We'll create a flag here to start our coordination. Once we
|
// define this flag to something other than just plain zero, then
|
// define this flag to something other than just plain zero, then
|
// the stalls will already be in place.
|
// the stalls will already be in place.
|
`define DONT_STALL_ON_OPA
|
`define DONT_STALL_ON_OPA
|
`ifdef DONT_STALL_ON_OPA
|
`ifdef DONT_STALL_ON_OPA
|
reg opA_alu;
|
reg opA_alu;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce)
|
if (op_ce)
|
opA_alu <= (opvalid_alu)&&(opR == dcdA)&&(dcdA_rd);
|
opA_alu <= (opvalid_alu)&&(opR == dcdA)&&(dcdA_rd);
|
assign opA = (opA_alu) ? alu_result : r_opA;
|
assign opA = (opA_alu) ? alu_result : r_opA;
|
`else
|
`else
|
assign opA = r_opA;
|
assign opA = r_opA;
|
`endif
|
`endif
|
|
|
assign dcdA_stall = (dcdvalid)&&(dcdA_rd)&&(
|
assign dcdA_stall = (dcdvalid)&&(dcdA_rd)&&(
|
`define DONT_STALL_ON_OPB
|
`define DONT_STALL_ON_OPA
|
`ifdef DONT_STALL_ON_OPB
|
`ifdef DONT_STALL_ON_OPA
|
// Skip the requirement on writing back opA
|
// Skip the requirement on writing back opA
|
// Stall on memory, since we'll always need to stall for a
|
// Stall on memory, since we'll always need to stall for a
|
// memory access anyway
|
// memory access anyway
|
((opvalid_mem)&&(opR_wr)&&(opR == dcdA))||
|
((opvalid_mem)&&(opR_wr)&&(opR == dcdA))||
|
|
((opvalid_alu)&&(opF_wr)&&(dcdA_cc))||
|
`else
|
`else
|
((opvalid)&&(opR_wr)&&(opR == dcdA))||
|
((opvalid)&&(opR_wr)&&(opR == dcdA))||
|
`endif
|
`endif
|
((mem_busy)&&(~mem_we)&&(mem_wreg == dcdA)));
|
((mem_busy)&&(~mem_we)&&(mem_wreg == dcdA)));
|
|
`define DONT_STALL_ON_OPB
|
`ifdef DONT_STALL_ON_OPB
|
`ifdef DONT_STALL_ON_OPB
|
reg opB_alu;
|
reg opB_alu;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (op_ce)
|
if (op_ce)
|
opB_alu <= (opvalid_alu)&&(opR == dcdB)&&(dcdB_rd)&&(dcdI == 0);
|
opB_alu <= (opvalid_alu)&&(opR == dcdB)&&(dcdB_rd)&&(dcdI == 0);
|
assign opB = (opB_alu) ? alu_result : r_opB;
|
assign opB = (opB_alu) ? alu_result : r_opB;
|
`else
|
`else
|
assign opB = r_opB;
|
assign opB = r_opB;
|
`endif
|
`endif
|
assign dcdB_stall = (dcdvalid)&&(dcdB_rd)&&(
|
assign dcdB_stall = (dcdvalid)&&(dcdB_rd)&&(
|
((opvalid)&&(opR_wr)&&(opR == dcdB)
|
((opvalid)&&(opR_wr)&&(opR == dcdB)
|
|
&&((opvalid_mem)||(dcdI != 0)))
|
|
||((opvalid_alu)&&(opF_wr)&&(dcdB_cc))
|
`ifdef DONT_STALL_ON_OPB
|
`ifdef DONT_STALL_ON_OPB
|
&&((opvalid_mem)||(dcdI != 0))
|
|
`endif
|
`endif
|
)||
|
||((mem_busy)&&(~mem_we)&&(mem_wreg == dcdB)));
|
((mem_busy)&&(~mem_we)&&(mem_wreg == dcdB)));
|
assign dcdF_stall = (dcdvalid)&&((~dcdF[3])||(dcdA_cc)||(dcdB_cc))
|
assign dcdF_stall = (dcdvalid)&&(
|
&&(opvalid)&&(opR_cc);
|
(((~dcdF[3]) ||(dcdA_cc) ||(dcdB_cc))
|
|
&&(opvalid)&&((opR_cc)||(opF_wr)))
|
|
||((dcdF[3])&&(dcdM)&&(opvalid)&&(opF_wr)));
|
|
//
|
//
|
//
|
//
|
// PIPELINE STAGE #4 :: Apply Instruction
|
// PIPELINE STAGE #4 :: Apply Instruction
|
//
|
//
|
//
|
//
|
cpuops doalu(i_clk, i_rst, alu_ce,
|
cpuops doalu(i_clk, i_rst, alu_ce,
|
(opvalid_alu), opn, opA, opB,
|
(opvalid_alu), opn, opA, opB,
|
alu_result, alu_flags, alu_valid);
|
alu_result, alu_flags, alu_valid);
|
|
|
assign set_cond = ((opF[7:4]&opFl[3:0])==opF[3:0]);
|
assign set_cond = ((opF[7:4]&opFl[3:0])==opF[3:0]);
|
initial alF_wr = 1'b0;
|
initial alF_wr = 1'b0;
|
initial alu_wr = 1'b0;
|
initial alu_wr = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
begin
|
begin
|
alu_wr <= 1'b0;
|
alu_wr <= 1'b0;
|
alF_wr <= 1'b0;
|
alF_wr <= 1'b0;
|
end else if (alu_ce)
|
end else if (alu_ce)
|
begin
|
begin
|
alu_reg <= opR;
|
alu_reg <= opR;
|
alu_wr <= (opR_wr)&&(set_cond);
|
alu_wr <= (opR_wr)&&(set_cond);
|
alF_wr <= (opF_wr)&&(set_cond);
|
alF_wr <= (opF_wr)&&(set_cond);
|
end else begin
|
end else begin
|
// These are strobe signals, so clear them if not
|
// These are strobe signals, so clear them if not
|
// set for any particular clock
|
// set for any particular clock
|
alu_wr <= 1'b0;
|
alu_wr <= 1'b0;
|
alF_wr <= 1'b0;
|
alF_wr <= 1'b0;
|
end
|
end
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((alu_ce)||(mem_ce))
|
if ((alu_ce)||(mem_ce))
|
alu_gie <= op_gie;
|
alu_gie <= op_gie;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((alu_ce)||(mem_ce))
|
if ((alu_ce)||(mem_ce))
|
alu_pc <= op_pc;
|
alu_pc <= op_pc;
|
initial alu_pc_valid = 1'b0;
|
initial alu_pc_valid = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
alu_pc_valid <= (~i_rst)&&(master_ce)&&(opvalid)&&(~clear_pipeline)
|
alu_pc_valid <= (~i_rst)&&(master_ce)&&(opvalid)&&(~clear_pipeline)
|
&&((opvalid_alu)||(~mem_stalled));
|
&&((opvalid_alu)||(~mem_stalled));
|
|
|
memops domem(i_clk, i_rst, mem_ce,
|
memops domem(i_clk, i_rst, mem_ce,
|
(opn[0]), opB, opA, opR,
|
(opn[0]), opB, opA, opR,
|
mem_busy, mem_valid, mem_wreg, mem_result,
|
mem_busy, mem_valid, mem_wreg, mem_result,
|
mem_cyc, mem_stb, mem_we, mem_addr, mem_data,
|
mem_cyc, mem_stb, mem_we, mem_addr, mem_data,
|
mem_ack, mem_stall, i_wb_data);
|
mem_ack, mem_stall, i_wb_data);
|
assign mem_rdbusy = ((mem_cyc)&&(~mem_we));
|
assign mem_rdbusy = ((mem_cyc)&&(~mem_we));
|
|
|
// Either the prefetch or the instruction gets the memory bus, but
|
// Either the prefetch or the instruction gets the memory bus, but
|
// never both.
|
// never both.
|
wbarbiter #(32,32) pformem(i_clk, i_rst,
|
wbarbiter #(32,32) pformem(i_clk, i_rst,
|
// Prefetch access to the arbiter
|
// Prefetch access to the arbiter
|
pf_addr, pf_data, pf_we, pf_stb, pf_cyc, pf_ack, pf_stall,
|
pf_addr, pf_data, pf_we, pf_stb, pf_cyc, pf_ack, pf_stall,
|
// Memory access to the arbiter
|
// Memory access to the arbiter
|
mem_addr, mem_data, mem_we, mem_stb, mem_cyc, mem_ack, mem_stall,
|
mem_addr, mem_data, mem_we, mem_stb, mem_cyc, mem_ack, mem_stall,
|
// Common wires, in and out, of the arbiter
|
// Common wires, in and out, of the arbiter
|
o_wb_addr, o_wb_data, o_wb_we, o_wb_stb, o_wb_cyc, i_wb_ack,
|
o_wb_addr, o_wb_data, o_wb_we, o_wb_stb, o_wb_cyc, i_wb_ack,
|
i_wb_stall);
|
i_wb_stall);
|
|
|
//
|
//
|
//
|
//
|
// PIPELINE STAGE #5 :: Write-back results
|
// PIPELINE STAGE #5 :: Write-back results
|
//
|
//
|
//
|
//
|
// This stage is not allowed to stall. If results are ready to be
|
// This stage is not allowed to stall. If results are ready to be
|
// written back, they are written back at all cost. Sleepy CPU's
|
// written back, they are written back at all cost. Sleepy CPU's
|
// won't prevent write back, nor debug modes, halting the CPU, nor
|
// won't prevent write back, nor debug modes, halting the CPU, nor
|
// anything else. Indeed, the (master_ce) bit is only as relevant
|
// anything else. Indeed, the (master_ce) bit is only as relevant
|
// as knowinig something is available for writeback.
|
// as knowinig something is available for writeback.
|
|
|
//
|
//
|
// Write back to our generic register set ...
|
// Write back to our generic register set ...
|
// When shall we write back? On one of two conditions
|
// When shall we write back? On one of two conditions
|
// Note that the flags needed to be checked before issuing the
|
// Note that the flags needed to be checked before issuing the
|
// bus instruction, so they don't need to be checked here.
|
// bus instruction, so they don't need to be checked here.
|
// Further, alu_wr includes (set_cond), so we don't need to
|
// Further, alu_wr includes (set_cond), so we don't need to
|
// check for that here either.
|
// check for that here either.
|
assign wr_reg_ce = ((alu_wr)&&(alu_valid))||(mem_valid);
|
assign wr_reg_ce = ((alu_wr)&&(alu_valid))||(mem_valid);
|
// Which register shall be written?
|
// Which register shall be written?
|
assign wr_reg_id = (alu_wr)?alu_reg:mem_wreg;
|
assign wr_reg_id = (alu_wr)?alu_reg:mem_wreg;
|
// Are we writing to the CC register?
|
// Are we writing to the CC register?
|
assign wr_write_cc = (wr_reg_id[3:0] == `CPU_CC_REG);
|
assign wr_write_cc = (wr_reg_id[3:0] == `CPU_CC_REG);
|
// Are we writing to the PC?
|
// Are we writing to the PC?
|
assign wr_write_pc = (wr_reg_id[3:0] == `CPU_PC_REG);
|
assign wr_write_pc = (wr_reg_id[3:0] == `CPU_PC_REG);
|
// What value to write?
|
// What value to write?
|
assign wr_reg_vl = (alu_wr)?alu_result:mem_result;
|
assign wr_reg_vl = (alu_wr)?alu_result:mem_result;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (wr_reg_ce)
|
if (wr_reg_ce)
|
regset[wr_reg_id] <= wr_reg_vl;
|
regset[wr_reg_id] <= wr_reg_vl;
|
else if ((i_halt)&&(i_dbg_we))
|
else if ((i_halt)&&(i_dbg_we))
|
regset[i_dbg_reg] <= i_dbg_data[31:0];
|
regset[i_dbg_reg] <= i_dbg_data[31:0];
|
|
|
//
|
//
|
// Write back to the condition codes/flags register ...
|
// Write back to the condition codes/flags register ...
|
// When shall we write to our flags register? alF_wr already
|
// When shall we write to our flags register? alF_wr already
|
// includes the set condition ...
|
// includes the set condition ...
|
assign wr_flags_ce = (alF_wr)&&(alu_valid);
|
assign wr_flags_ce = (alF_wr)&&(alu_valid);
|
assign w_uflags = { trap, 1'b0, 1'b0, step, 1'b1, sleep, ((wr_flags_ce)&&(alu_gie))?alu_flags:flags };
|
assign w_uflags = { trap, 1'b0, 1'b0, step, 1'b1, sleep, ((wr_flags_ce)&&(alu_gie))?alu_flags:flags };
|
assign w_iflags = { trap, 1'b0, break_en, 1'b0, 1'b0, sleep, ((wr_flags_ce)&&(~alu_gie))?alu_flags:iflags };
|
assign w_iflags = { trap, 1'b0, break_en, 1'b0, 1'b0, sleep, ((wr_flags_ce)&&(~alu_gie))?alu_flags:iflags };
|
// What value to write?
|
// What value to write?
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
// If explicitly writing the register itself
|
// If explicitly writing the register itself
|
if ((wr_reg_ce)&&(wr_reg_id[4])&&(wr_write_cc))
|
if ((wr_reg_ce)&&(wr_reg_id[4])&&(wr_write_cc))
|
flags <= wr_reg_vl[3:0];
|
flags <= wr_reg_vl[3:0];
|
// Otherwise if we're setting the flags from an ALU operation
|
// Otherwise if we're setting the flags from an ALU operation
|
else if ((wr_flags_ce)&&(alu_gie))
|
else if ((wr_flags_ce)&&(alu_gie))
|
flags <= alu_flags;
|
flags <= alu_flags;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
flags <= i_dbg_data[3:0];
|
flags <= i_dbg_data[3:0];
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_cc))
|
if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_cc))
|
iflags <= wr_reg_vl[3:0];
|
iflags <= wr_reg_vl[3:0];
|
else if ((wr_flags_ce)&&(~alu_gie))
|
else if ((wr_flags_ce)&&(~alu_gie))
|
iflags <= alu_flags;
|
iflags <= alu_flags;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b0, `CPU_CC_REG }))
|
&&(i_dbg_reg == { 1'b0, `CPU_CC_REG }))
|
iflags <= i_dbg_data[3:0];
|
iflags <= i_dbg_data[3:0];
|
|
|
// The 'break' enable bit. This bit can only be set from supervisor
|
// The 'break' enable bit. This bit can only be set from supervisor
|
// mode. It control what the CPU does upon encountering a break
|
// mode. It control what the CPU does upon encountering a break
|
// instruction.
|
// instruction.
|
//
|
//
|
// The goal, upon encountering a break is that the CPU should stop and
|
// The goal, upon encountering a break is that the CPU should stop and
|
// not execute the break instruction, choosing instead to enter into
|
// not execute the break instruction, choosing instead to enter into
|
// either interrupt mode or halt first.
|
// either interrupt mode or halt first.
|
// if ((break_en) AND (break_instruction)) // user mode or not
|
// if ((break_en) AND (break_instruction)) // user mode or not
|
// HALT CPU
|
// HALT CPU
|
// else if (break_instruction) // only in user mode
|
// else if (break_instruction) // only in user mode
|
// set an interrupt flag, go to supervisor mode
|
// set an interrupt flag, go to supervisor mode
|
// allow supervisor to step the CPU.
|
// allow supervisor to step the CPU.
|
// Upon a CPU halt, any break condition will be reset. The
|
// Upon a CPU halt, any break condition will be reset. The
|
// external debugger will then need to deal with whatever
|
// external debugger will then need to deal with whatever
|
// condition has taken place.
|
// condition has taken place.
|
initial break_en = 1'b0;
|
initial break_en = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((i_rst)||(i_halt))
|
if ((i_rst)||(i_halt))
|
break_en <= 1'b0;
|
break_en <= 1'b0;
|
else if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_cc))
|
else if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_cc))
|
break_en <= wr_reg_vl[`CPU_BREAK_BIT];
|
break_en <= wr_reg_vl[`CPU_BREAK_BIT];
|
assign o_break = ((break_en)||(~op_gie))&&(op_break)&&(~alu_valid)&&(~mem_valid)&&(~mem_busy);
|
assign o_break = ((break_en)||(~op_gie))&&(op_break)&&(~alu_valid)&&(~mem_valid)&&(~mem_busy);
|
|
|
|
|
// The sleep register. Setting the sleep register causes the CPU to
|
// The sleep register. Setting the sleep register causes the CPU to
|
// sleep until the next interrupt. Setting the sleep register within
|
// sleep until the next interrupt. Setting the sleep register within
|
// interrupt mode causes the processor to halt until a reset. This is
|
// interrupt mode causes the processor to halt until a reset. This is
|
// a panic/fault halt. The trick is that you cannot be allowed to
|
// a panic/fault halt. The trick is that you cannot be allowed to
|
// set the sleep bit and switch to supervisor mode in the same
|
// set the sleep bit and switch to supervisor mode in the same
|
// instruction: users are not allowed to halt the CPU.
|
// instruction: users are not allowed to halt the CPU.
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((i_rst)||((i_interrupt)&&(gie)))
|
if ((i_rst)||((i_interrupt)&&(gie)))
|
sleep <= 1'b0;
|
sleep <= 1'b0;
|
else if ((wr_reg_ce)&&(wr_write_cc)&&(~alu_gie))
|
else if ((wr_reg_ce)&&(wr_write_cc)&&(~alu_gie))
|
// In supervisor mode, we have no protections. The
|
// In supervisor mode, we have no protections. The
|
// supervisor can set the sleep bit however he wants.
|
// supervisor can set the sleep bit however he wants.
|
sleep <= wr_reg_vl[`CPU_SLEEP_BIT];
|
sleep <= wr_reg_vl[`CPU_SLEEP_BIT];
|
else if ((wr_reg_ce)&&(wr_write_cc)&&(wr_reg_vl[`CPU_GIE_BIT]))
|
else if ((wr_reg_ce)&&(wr_write_cc)&&(wr_reg_vl[`CPU_GIE_BIT]))
|
// In user mode, however, you can only set the sleep
|
// In user mode, however, you can only set the sleep
|
// mode while remaining in user mode. You can't switch
|
// mode while remaining in user mode. You can't switch
|
// to sleep mode *and* supervisor mode at the same
|
// to sleep mode *and* supervisor mode at the same
|
// time, lest you halt the CPU.
|
// time, lest you halt the CPU.
|
sleep <= wr_reg_vl[`CPU_SLEEP_BIT];
|
sleep <= wr_reg_vl[`CPU_SLEEP_BIT];
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
sleep <= i_dbg_data[`CPU_SLEEP_BIT];
|
sleep <= i_dbg_data[`CPU_SLEEP_BIT];
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((i_rst)||(w_switch_to_interrupt))
|
if ((i_rst)||(w_switch_to_interrupt))
|
step <= 1'b0;
|
step <= 1'b0;
|
else if ((wr_reg_ce)&&(~alu_gie)&&(wr_reg_id[4])&&(wr_write_cc))
|
else if ((wr_reg_ce)&&(~alu_gie)&&(wr_reg_id[4])&&(wr_write_cc))
|
step <= wr_reg_vl[`CPU_STEP_BIT];
|
step <= wr_reg_vl[`CPU_STEP_BIT];
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG }))
|
step <= i_dbg_data[`CPU_STEP_BIT];
|
step <= i_dbg_data[`CPU_STEP_BIT];
|
else if ((master_ce)&&(alu_pc_valid)&&(step)&&(gie))
|
else if ((master_ce)&&(alu_pc_valid)&&(step)&&(gie))
|
step <= 1'b0;
|
step <= 1'b0;
|
|
|
// The GIE register. Only interrupts can disable the interrupt register
|
// The GIE register. Only interrupts can disable the interrupt register
|
assign w_switch_to_interrupt = (gie)&&(
|
assign w_switch_to_interrupt = (gie)&&(
|
// On interrupt (obviously)
|
// On interrupt (obviously)
|
(i_interrupt)
|
(i_interrupt)
|
// If we are stepping the CPU
|
// If we are stepping the CPU
|
||((master_ce)&&(alu_pc_valid)&&(step))
|
||((master_ce)&&(alu_pc_valid)&&(step))
|
// If we encounter a break instruction, if the break
|
// If we encounter a break instruction, if the break
|
// enable isn't not set.
|
// enable isn't not set.
|
||((master_ce)&&(op_break)&&(~break_en))
|
||((master_ce)&&(op_break)&&(~break_en))
|
// If we write to the CC register
|
// If we write to the CC register
|
||((wr_reg_ce)&&(~wr_reg_vl[`CPU_GIE_BIT])
|
||((wr_reg_ce)&&(~wr_reg_vl[`CPU_GIE_BIT])
|
&&(wr_reg_id[4])&&(wr_write_cc))
|
&&(wr_reg_id[4])&&(wr_write_cc))
|
// Or if, in debug mode, we write to the CC register
|
// Or if, in debug mode, we write to the CC register
|
||((i_halt)&&(i_dbg_we)&&(~i_dbg_data[`CPU_GIE_BIT])
|
||((i_halt)&&(i_dbg_we)&&(~i_dbg_data[`CPU_GIE_BIT])
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG}))
|
&&(i_dbg_reg == { 1'b1, `CPU_CC_REG}))
|
);
|
);
|
assign w_release_from_interrupt = (~gie)&&(~i_interrupt)
|
assign w_release_from_interrupt = (~gie)&&(~i_interrupt)
|
// Then if we write the CC register
|
// Then if we write the CC register
|
&&(((wr_reg_ce)&&(wr_reg_vl[`CPU_GIE_BIT])
|
&&(((wr_reg_ce)&&(wr_reg_vl[`CPU_GIE_BIT])
|
&&(~wr_reg_id[4])&&(wr_write_cc))
|
&&(~wr_reg_id[4])&&(wr_write_cc))
|
// Or if, in debug mode, we write the CC register
|
// Or if, in debug mode, we write the CC register
|
||((i_halt)&&(i_dbg_we)&&(i_dbg_data[`CPU_GIE_BIT])
|
||((i_halt)&&(i_dbg_we)&&(i_dbg_data[`CPU_GIE_BIT])
|
&&(i_dbg_reg == { 1'b0, `CPU_CC_REG}))
|
&&(i_dbg_reg == { 1'b0, `CPU_CC_REG}))
|
);
|
);
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
gie <= 1'b0;
|
gie <= 1'b0;
|
else if (w_switch_to_interrupt)
|
else if (w_switch_to_interrupt)
|
gie <= 1'b0;
|
gie <= 1'b0;
|
else if (w_release_from_interrupt)
|
else if (w_release_from_interrupt)
|
gie <= 1'b1;
|
gie <= 1'b1;
|
|
|
initial trap = 1'b0;
|
initial trap = 1'b0;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
trap <= 1'b0;
|
trap <= 1'b0;
|
else if ((gie)&&(wr_reg_ce)&&(~wr_reg_vl[`CPU_GIE_BIT])
|
else if ((gie)&&(wr_reg_ce)&&(~wr_reg_vl[`CPU_GIE_BIT])
|
&&(wr_reg_id[4])&&(wr_write_cc))
|
&&(wr_reg_id[4])&&(wr_write_cc))
|
trap <= 1'b1;
|
trap <= 1'b1;
|
else if ((i_halt)&&(i_dbg_we)&&(i_dbg_reg[3:0] == `CPU_CC_REG)
|
else if ((i_halt)&&(i_dbg_we)&&(i_dbg_reg[3:0] == `CPU_CC_REG)
|
&&(~i_dbg_data[`CPU_GIE_BIT]))
|
&&(~i_dbg_data[`CPU_GIE_BIT]))
|
trap <= i_dbg_data[`CPU_TRAP_BIT];
|
trap <= i_dbg_data[`CPU_TRAP_BIT];
|
else if (w_release_from_interrupt)
|
else if (w_release_from_interrupt)
|
trap <= 1'b0;
|
trap <= 1'b0;
|
|
|
//
|
//
|
// Write backs to the PC register, and general increments of it
|
// Write backs to the PC register, and general increments of it
|
// We support two: upc and ipc. If the instruction is normal,
|
// We support two: upc and ipc. If the instruction is normal,
|
// we increment upc, if interrupt level we increment ipc. If
|
// we increment upc, if interrupt level we increment ipc. If
|
// the instruction writes the PC, we write whichever PC is appropriate.
|
// the instruction writes the PC, we write whichever PC is appropriate.
|
//
|
//
|
// Do we need to all our partial results from the pipeline?
|
// Do we need to all our partial results from the pipeline?
|
// What happens when the pipeline has gie and ~gie instructions within
|
// What happens when the pipeline has gie and ~gie instructions within
|
// it? Do we clear both? What if a gie instruction tries to clear
|
// it? Do we clear both? What if a gie instruction tries to clear
|
// a non-gie instruction?
|
// a non-gie instruction?
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((wr_reg_ce)&&(wr_reg_id[4])&&(wr_write_pc))
|
if ((wr_reg_ce)&&(wr_reg_id[4])&&(wr_write_pc))
|
upc <= wr_reg_vl;
|
upc <= wr_reg_vl;
|
else if ((alu_gie)&&(alu_pc_valid))
|
else if ((alu_gie)&&(alu_pc_valid))
|
upc <= alu_pc;
|
upc <= alu_pc;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b1, `CPU_PC_REG }))
|
&&(i_dbg_reg == { 1'b1, `CPU_PC_REG }))
|
upc <= i_dbg_data;
|
upc <= i_dbg_data;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
ipc <= RESET_ADDRESS;
|
ipc <= RESET_ADDRESS;
|
else if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_pc))
|
else if ((wr_reg_ce)&&(~wr_reg_id[4])&&(wr_write_pc))
|
ipc <= wr_reg_vl;
|
ipc <= wr_reg_vl;
|
else if ((~alu_gie)&&(alu_pc_valid))
|
else if ((~alu_gie)&&(alu_pc_valid))
|
ipc <= alu_pc;
|
ipc <= alu_pc;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(i_dbg_reg == { 1'b0, `CPU_PC_REG }))
|
&&(i_dbg_reg == { 1'b0, `CPU_PC_REG }))
|
ipc <= i_dbg_data;
|
ipc <= i_dbg_data;
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if (i_rst)
|
if (i_rst)
|
pf_pc <= RESET_ADDRESS;
|
pf_pc <= RESET_ADDRESS;
|
else if (w_switch_to_interrupt)
|
else if (w_switch_to_interrupt)
|
pf_pc <= ipc;
|
pf_pc <= ipc;
|
else if (w_release_from_interrupt)
|
else if (w_release_from_interrupt)
|
pf_pc <= upc;
|
pf_pc <= upc;
|
else if ((wr_reg_ce)&&(wr_reg_id[4] == gie)&&(wr_write_pc))
|
else if ((wr_reg_ce)&&(wr_reg_id[4] == gie)&&(wr_write_pc))
|
pf_pc <= wr_reg_vl;
|
pf_pc <= wr_reg_vl;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(wr_reg_id[4:0] == { gie, `CPU_PC_REG}))
|
&&(wr_reg_id[4:0] == { gie, `CPU_PC_REG}))
|
pf_pc <= i_dbg_data;
|
pf_pc <= i_dbg_data;
|
else if (dcd_ce)
|
else if (dcd_ce)
|
pf_pc <= pf_pc + 1;
|
pf_pc <= pf_pc + 1;
|
|
|
initial new_pc = 1'b1;
|
initial new_pc = 1'b1;
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
if ((i_rst)||(i_clear_pf_cache))
|
if ((i_rst)||(i_clear_pf_cache))
|
new_pc <= 1'b1;
|
new_pc <= 1'b1;
|
else if (w_switch_to_interrupt)
|
else if (w_switch_to_interrupt)
|
new_pc <= 1'b1;
|
new_pc <= 1'b1;
|
else if (w_release_from_interrupt)
|
else if (w_release_from_interrupt)
|
new_pc <= 1'b1;
|
new_pc <= 1'b1;
|
else if ((wr_reg_ce)&&(wr_reg_id[4] == gie)&&(wr_write_pc))
|
else if ((wr_reg_ce)&&(wr_reg_id[4] == gie)&&(wr_write_pc))
|
new_pc <= 1'b1;
|
new_pc <= 1'b1;
|
else if ((i_halt)&&(i_dbg_we)
|
else if ((i_halt)&&(i_dbg_we)
|
&&(wr_reg_id[4:0] == { gie, `CPU_PC_REG}))
|
&&(wr_reg_id[4:0] == { gie, `CPU_PC_REG}))
|
new_pc <= 1'b1;
|
new_pc <= 1'b1;
|
else
|
else
|
new_pc <= 1'b0;
|
new_pc <= 1'b0;
|
|
|
//
|
//
|
// The debug interface
|
// The debug interface
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
begin
|
begin
|
o_dbg_reg <= regset[i_dbg_reg];
|
o_dbg_reg <= regset[i_dbg_reg];
|
if (i_dbg_reg[3:0] == `CPU_PC_REG)
|
if (i_dbg_reg[3:0] == `CPU_PC_REG)
|
o_dbg_reg <= (i_dbg_reg[4])?upc:ipc;
|
o_dbg_reg <= (i_dbg_reg[4])?upc:ipc;
|
else if (i_dbg_reg[3:0] == `CPU_CC_REG)
|
else if (i_dbg_reg[3:0] == `CPU_CC_REG)
|
o_dbg_reg[9:0] <= (i_dbg_reg[4])?w_uflags:w_iflags;
|
o_dbg_reg[9:0] <= (i_dbg_reg[4])?w_uflags:w_iflags;
|
end
|
end
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
o_dbg_cc <= { gie, sleep };
|
o_dbg_cc <= { gie, sleep };
|
|
|
always @(posedge i_clk)
|
always @(posedge i_clk)
|
o_dbg_stall <= (i_halt)&&(
|
o_dbg_stall <= (i_halt)&&(
|
(pf_cyc)||(mem_cyc)||(mem_busy)
|
(pf_cyc)||(mem_cyc)||(mem_busy)
|
||((~opvalid)&&(~i_rst))
|
||((~opvalid)&&(~i_rst))
|
||((~dcdvalid)&&(~i_rst)));
|
||((~dcdvalid)&&(~i_rst)));
|
|
|
//
|
//
|
//
|
//
|
// Produce accounting outputs: Account for any CPU stalls, so we can
|
// Produce accounting outputs: Account for any CPU stalls, so we can
|
// later evaluate how well we are doing.
|
// later evaluate how well we are doing.
|
//
|
//
|
//
|
//
|
assign o_op_stall = (master_ce)&&((~opvalid)||(op_stall));
|
assign o_op_stall = (master_ce)&&((~opvalid)||(op_stall));
|
assign o_pf_stall = (master_ce)&&(~pf_valid);
|
assign o_pf_stall = (master_ce)&&(~pf_valid);
|
assign o_i_count = alu_pc_valid;
|
assign o_i_count = alu_pc_valid;
|
endmodule
|
endmodule
|
|
|
