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jshamlet |
-- Copyright (c)2006, 2011, 2012, 2013, 2015, 2019, 2020 Jeremy Seth Henry
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jshamlet |
-- All rights reserved.
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--
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-- Redistribution and use in source and binary forms, with or without
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-- modification, are permitted provided that the following conditions are met:
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-- * Redistributions of source code must retain the above copyright
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-- notice, this list of conditions and the following disclaimer.
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-- * Redistributions in binary form must reproduce the above copyright
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-- notice, this list of conditions and the following disclaimer in the
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-- documentation and/or other materials provided with the distribution,
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-- where applicable (as part of a user interface, debugging port, etc.)
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--
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-- THIS SOFTWARE IS PROVIDED BY JEREMY SETH HENRY ``AS IS'' AND ANY
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-- EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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-- WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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-- DISCLAIMED. IN NO EVENT SHALL JEREMY SETH HENRY BE LIABLE FOR ANY
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-- DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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-- (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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-- LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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-- ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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jshamlet |
-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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-- THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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jshamlet |
--
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jshamlet |
-- VHDL Units : o8_cpu
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jshamlet |
-- Description: VHDL model of a RISC 8-bit processor core loosely based on the
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-- : V8/ARC uRISC instruction set. Requires Open8_pkg.vhd
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-- :
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-- Notes : Generic definitions
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-- :
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-- : Program_Start_Addr sets the initial value of the program
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-- : counter.
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-- :
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-- : ISR_Start_Addr sets the location of the interrupt service
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-- : vector table. There are 8 service vectors, or 16 bytes, which
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-- : must be allocated to either ROM or RAM.
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-- :
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-- : Stack_Start_Address sets the initial (reset) value of the
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-- : stack pointer. Also used for the RSP instruction if
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-- : Allow_Stack_Address_Move is false.
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-- :
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-- : Allow_Stack_Address_Move, when set true, allows the RSP to be
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-- : programmed via thet RSP instruction. If enabled, the
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-- : instruction changes into TSX or TXS based on the flag
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-- : specified by Stack_Xfer_Flag. If the flag is '0', RSP will
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-- : copy the current stack pointer to R1:R0 (TSX). If the flag
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-- : is '1', RSP will copy R1:R0 to the stack pointer (TXS). This
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-- : allows the processor to backup and restore stack pointers
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-- : in a multi-process environment. Note that no flags are
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-- : modified by either form of this instruction.
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-- :
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-- : Stack_Xfer_Flag instructs the core to use the specified ALU
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-- : flag to alter the behavior of the RSP instruction when
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-- : Allow_Stack_Address_Move is set TRUE, otherwise it is ignored.
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-- : While technically any of the status bits may be used, the
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-- : intent was to use FL_GP[1,2,3,4], as these are not modified
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-- : by ordinary ALU operations.
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-- :
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-- : The Enable_Auto_Increment generic can be used to modify the
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-- : indexed instructions such that specifying an odd register
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-- : will use the next lower register pair, post-incrementing the
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-- : value in that pair. IOW, specifying STX R1 will instead
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-- : result in STX R0++, or R0 = {R1:R0}; {R1:R0} + 1
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-- :
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-- : BRK_Implements_WAI modifies the BRK instruction such that it
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-- : triggers the wait for interrupt state, but without triggering
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-- : a soft interrupt in lieu of its normal behavior, which is to
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-- : insert several dead clock cycles - essentially a long NOP
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-- :
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-- : Enable_NMI overrides the mask bit for interrupt 0, creating a
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-- : non-maskable interrupt at the highest priority. To remain
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-- : true to the original core, this should be set false.
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-- :
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-- : RTI_Ignores_GP_Flags alters the set of flag bits restored
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-- : after an interrupt. By default, all of the flag bits are put
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-- : back to their original state. If this flag is set true, only
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-- : the lower four bits are restored, allowing ISR code to alter
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-- : the GP flags persistently.
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-- :
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-- : Supervisor_Mode, when set, disables the STP PSR_I instruction
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-- : preventing code from setting the I bit. When enabled, only
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-- : interrupts can set the I bit, allowing for more robust memory
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-- : protection by preventing errant code execution from
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-- : inadvertently entering an interrupt state.
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-- :
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-- : This setting also sets I bit at startup so that any
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-- : initialization code may be run in an ISR context, initially
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-- : bypassing memory protection. Init code should clear the I bit
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-- : when done;
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jshamlet |
-- :
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jshamlet |
-- : Default_Interrupt_Mask sets the intial/reset value of the
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-- : interrupt mask. To remain true to the original core, which
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-- : had no interrupt mask, this should be set to x"FF". Otherwise
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-- : it can be initialized to any value. Note that Enable_NMI
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-- : will logically force the LSB high.
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-- :
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-- : Reset_Level determines whether the processor registers reset
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-- : on a high or low level from higher logic.
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-- :
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-- : Architecture notes
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-- : This model deviates from the original ISA in a few important
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-- : ways.
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-- :
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-- : First, there is only one set of registers. Interrupt service
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-- : routines must explicitely preserve context since the the
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-- : hardware doesn't. This was done to decrease size and code
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-- : complexity. Older code that assumes this behavior will not
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-- : execute correctly on this processor model.
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-- :
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-- : Second, this model adds an additional pipeline stage between
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-- : the instruction decoder and the ALU. Unfortunately, this
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-- : means that the instruction stream has to be restarted after
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-- : any math instruction is executed, implying that any ALU
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-- : instruction now has a latency of 2 instead of 0. The
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-- : advantage is that the maximum frequency has gone up
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-- : significantly, as the ALU code is vastly more efficient.
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-- : As an aside, this now means that all math instructions,
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-- : including MUL (see below) and UPP have the same instruction
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-- : latency.
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-- :
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-- : Third, the original ISA, also a soft core, had two reserved
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-- : instructions, USR and USR2. These have been implemented as
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-- : DBNZ, and MUL respectively.
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-- :
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-- : DBNZ decrements the specified register and branches if the
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-- : result is non-zero. The instruction effectively executes a
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-- : DEC Rn instruction prior to branching, so the same flags will
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-- : be set.
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-- :
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-- : MUL places the result of R0 * Rn into R1:R0. Instruction
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-- : latency is identical to other ALU instructions. Only the Z
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-- : flag is set, since there is no defined overflow or "negative
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-- : 16-bit values"
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-- :
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-- : Fourth, indexed load/store instructions now have an (optional)
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-- : ability to post-increment their index registers. If enabled,
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-- : using an odd operand for LDO,LDX, STO, STX will cause the
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-- : register pair to be incremented after the storage access.
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-- :
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-- : Fifth, the RSP instruction has been (optionally) altered to
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-- : allow the stack pointer to be sourced from R1:R0.
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-- :
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-- : Sixth, the BRK instruction can optionally implement a WAI,
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-- : which is the same as the INT instruction without the soft
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-- : interrupt, as a way to put the processor to "sleep" until the
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-- : next external interrupt.
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-- :
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-- : Seventh, the original CPU model had 8 non-maskable interrupts
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-- : with priority. This model has the same 8 interrupts, but
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-- : allows software to mask them (with an additional option to
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-- : override the highest priority interrupt, making it the NMI.)
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-- :
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-- : Lastly, previous unmapped instructions in the OP_STK opcode
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-- : were repurposed to support a new interrupt mask.
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-- : SMSK and GMSK transfer the contents of R0 (accumulator)
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-- : to/from the interrupt mask register. SMSK is immediate, while
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-- : GMSK has the same overhead as a math instruction.
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--
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-- Revision History
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-- Author Date Change
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------------------ -------- ---------------------------------------------------
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-- Seth Henry 07/19/06 Design Start
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-- Seth Henry 01/18/11 Fixed BTT instruction to match V8
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-- Seth Henry 07/22/11 Fixed interrupt transition logic to avoid data
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-- corruption issues.
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-- Seth Henry 07/26/11 Optimized logic in ALU, stack pointer, and data
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-- path sections.
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-- Seth Henry 07/27/11 Optimized logic for timing, merged blocks into
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-- single entity.
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-- Seth Henry 09/20/11 Added BRK_Implements_WAI option, allowing the
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-- processor to wait for an interrupt instead of the
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-- normal BRK behavior.
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-- Seth Henry 12/20/11 Modified core to allow WAI_Cx state to idle
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-- the bus entirely (Rd_Enable is low)
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-- Seth Henry 02/03/12 Replaced complex interrupt controller with simpler,
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-- faster logic that simply does priority encoding.
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-- Seth Henry 08/06/13 Removed HALT functionality
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-- Seth Henry 10/29/15 Fixed inverted carry logic in CMP and SBC instrs
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-- Seth Henry 12/19/19 Renamed to o8_cpu to fit "theme"
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-- Seth Henry 03/09/20 Modified RSP instruction to work with a CPU flag
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-- allowing true backup/restore of the stack pointer
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-- Seth Henry 03/11/20 Split the address logic from the main state machine
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-- in order to simplify things and eliminate
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-- redundancies. Came across and fixed a problem with
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-- the STO instruction when Enable_Auto_Increment is
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-- NOT set.
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jshamlet |
-- Seth Henry 03/12/20 Rationalized the naming of the CPU flags to match
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-- the assembler names. Also fixed an issue where
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-- the I bit wasn't being cleared after interrupts.
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-- Simplified the program counter logic to only use
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-- the offset for increments, redefining the
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-- original modes as fixed offset values.
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-- Modified the ALU section with a new ALU operation
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-- for GMSK. This allowed the .data field to be
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-- removed and Operand1 used in its place, which
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-- simplified the logic a great deal.
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-- Seth Henry 03/16/20 Added CPU_Halt input back, only now as an input to
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-- the instruction decode state, where it acts as a
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-- modified form of the BRK instruction that holds
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-- state until CPU_Halt is deasserted. This has a
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-- much smaller impact on Fmax/complexity than the
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-- original clock enable, but imposes a mild impact
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-- due to the need to reset the instruction pipeline
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-- Seth Henry 03/17/20 Added generic to control whether RTI full restores
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-- the flags, including the general purpose ones, or
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-- only the core ALU flags (Z, N, and C). Also
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-- brought out copies of the GP flags for external
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-- connection.
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-- Seth Henry 04/09/20 Added a compile time setting to block interrupts
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-- while the I bit is set to avoid reentering ISRs
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-- This may slightly affect timing, as this will
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-- potentially block higher priority interrupts
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-- until the lower priority ISR returns or clears
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-- the I bit.
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-- Also added the I bit to the exported flags for
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-- use in memory protection schemes.
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jshamlet |
-- Seth Henry 04/16/20 Modified to use new Open8 bus record. Also added
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-- reset and usec_tick logic to drive utility
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-- signals. Also added Halt_Ack output.
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-- Seth Henry 05/20/20 Added two new generics to alter the way the I bit
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-- is handled. The Supervisor_Mode setting disables
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-- STP PSR_I from being executed, preventing it
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-- from being set outside of an ISR. The
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-- Default_Int_Flag setting allows the I bit to
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-- start set so that initialization code can run,
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-- but not be hijacked later to corrupt any memory
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-- write protection later.
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-- Seth Henry 05/21/20 Supervisor_Mode now protects the interrupt mask
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-- and stack pointer as well.
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-- Seth Henry 05/24/20 Removed the Default_Int_Flag, as it is covered by
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-- Supervisor_Mode. If Supervisor_Mode isn't set,
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-- code can simply use STP to set the bit
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jshamlet |
-- Seth Henry 06/09/20 Added ability to use unsigned index offsets for
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jshamlet |
-- LDO/STO. Also pipelined the address calculation
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jshamlet |
-- for indexed instructions, reducing the final
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-- address generator to a multiplexor fed only by
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-- registers.
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jshamlet |
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library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_unsigned.all;
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use ieee.std_logic_arith.all;
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use ieee.std_logic_misc.all;
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library work;
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jshamlet |
use work.Open8_pkg.all;
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jshamlet |
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jshamlet |
entity o8_cpu is
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jshamlet |
generic(
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Program_Start_Addr : ADDRESS_TYPE := x"0000"; -- Initial PC location
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ISR_Start_Addr : ADDRESS_TYPE := x"FFF0"; -- Bottom of ISR vec's
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Stack_Start_Addr : ADDRESS_TYPE := x"03FF"; -- Top of Stack
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Allow_Stack_Address_Move : boolean := false; -- Use Normal v8 RSP
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jshamlet |
Stack_Xfer_Flag : integer := PSR_GP4; -- GP4 modifies RSP
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jshamlet |
Enable_Auto_Increment : boolean := false; -- Modify indexed instr
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BRK_Implements_WAI : boolean := false; -- BRK -> Wait for Int
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Enable_NMI : boolean := true; -- Force INTR0 enabled
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jshamlet |
Sequential_Interrupts : boolean := false; -- Interruptable ISRs
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jshamlet |
RTI_Ignores_GP_Flags : boolean := false; -- RTI sets all flags
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jshamlet |
Supervisor_Mode : boolean := false; -- I bit is restricted
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jshamlet |
Unsigned_Index_Offsets : boolean := false; -- Offsets are signed
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jshamlet |
Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
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jshamlet |
Clock_Frequency : real -- Clock Frequency
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);
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jshamlet |
port(
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Clock : in std_logic;
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jshamlet |
PLL_Locked : in std_logic;
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jshamlet |
--
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jshamlet |
Halt_Req : in std_logic := '0';
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Halt_Ack : out std_logic;
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--
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jshamlet |
Open8_Bus : out OPEN8_BUS_TYPE;
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jshamlet |
Rd_Data : in DATA_TYPE;
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jshamlet |
Interrupts : in INTERRUPT_BUNDLE := x"00"
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);
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jshamlet |
end entity;
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jshamlet |
architecture behave of o8_cpu is
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jshamlet |
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jshamlet |
signal Reset_q : std_logic := Reset_Level;
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signal Reset : std_logic := Reset_Level;
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constant USEC_VAL : integer := integer(Clock_Frequency / 1000000.0);
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constant USEC_WDT : integer := ceil_log2(USEC_VAL - 1);
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constant USEC_DLY : std_logic_vector :=
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conv_std_logic_vector(USEC_VAL - 1, USEC_WDT);
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signal uSec_Cntr : std_logic_vector( USEC_WDT - 1 downto 0 );
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signal uSec_Tick : std_logic;
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jshamlet |
constant INT_VECTOR_0 : ADDRESS_TYPE := ISR_Start_Addr;
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constant INT_VECTOR_1 : ADDRESS_TYPE := ISR_Start_Addr+2;
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constant INT_VECTOR_2 : ADDRESS_TYPE := ISR_Start_Addr+4;
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constant INT_VECTOR_3 : ADDRESS_TYPE := ISR_Start_Addr+6;
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constant INT_VECTOR_4 : ADDRESS_TYPE := ISR_Start_Addr+8;
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|
|
constant INT_VECTOR_5 : ADDRESS_TYPE := ISR_Start_Addr+10;
|
295 |
|
|
constant INT_VECTOR_6 : ADDRESS_TYPE := ISR_Start_Addr+12;
|
296 |
|
|
constant INT_VECTOR_7 : ADDRESS_TYPE := ISR_Start_Addr+14;
|
297 |
|
|
|
298 |
187 |
jshamlet |
signal CPU_Next_State : CPU_STATES := IPF_C0;
|
299 |
|
|
signal CPU_State : CPU_STATES := IPF_C0;
|
300 |
169 |
jshamlet |
|
301 |
225 |
jshamlet |
signal CPU_Halt_Req : std_logic := '0';
|
302 |
|
|
signal CPU_Halt_Ack : std_logic := '0';
|
303 |
187 |
jshamlet |
|
304 |
169 |
jshamlet |
signal Cache_Ctrl : CACHE_MODES := CACHE_IDLE;
|
305 |
|
|
|
306 |
|
|
signal Opcode : OPCODE_TYPE := (others => '0');
|
307 |
|
|
signal SubOp, SubOp_p1 : SUBOP_TYPE := (others => '0');
|
308 |
|
|
|
309 |
|
|
signal Prefetch : DATA_TYPE := x"00";
|
310 |
|
|
signal Operand1, Operand2 : DATA_TYPE := x"00";
|
311 |
|
|
|
312 |
|
|
signal Instr_Prefetch : std_logic := '0';
|
313 |
|
|
|
314 |
|
|
signal PC_Ctrl : PC_CTRL_TYPE;
|
315 |
|
|
signal Program_Ctr : ADDRESS_TYPE := x"0000";
|
316 |
|
|
|
317 |
182 |
jshamlet |
signal ALU_Ctrl : ALU_CTRL_TYPE;
|
318 |
|
|
signal Regfile : REGFILE_TYPE;
|
319 |
|
|
signal Flags : FLAG_TYPE;
|
320 |
|
|
signal Mult : ADDRESS_TYPE := x"0000";
|
321 |
|
|
|
322 |
169 |
jshamlet |
signal SP_Ctrl : SP_CTRL_TYPE;
|
323 |
|
|
signal Stack_Ptr : ADDRESS_TYPE := x"0000";
|
324 |
|
|
|
325 |
|
|
signal DP_Ctrl : DATA_CTRL_TYPE;
|
326 |
|
|
|
327 |
|
|
signal INT_Ctrl : INT_CTRL_TYPE;
|
328 |
|
|
signal Ack_D, Ack_Q, Ack_Q1: std_logic := '0';
|
329 |
|
|
signal Int_Req, Int_Ack : std_logic := '0';
|
330 |
245 |
jshamlet |
signal Set_Mask : std_logic := '0';
|
331 |
169 |
jshamlet |
signal Int_Mask : DATA_TYPE := x"00";
|
332 |
|
|
signal ISR_Addr : ADDRESS_TYPE := x"0000";
|
333 |
|
|
signal i_Ints : INTERRUPT_BUNDLE := x"00";
|
334 |
|
|
signal Pending : INTERRUPT_BUNDLE := x"00";
|
335 |
|
|
signal Wait_for_FSM : std_logic := '0';
|
336 |
210 |
jshamlet |
signal Wait_for_ISR : std_logic := '0';
|
337 |
169 |
jshamlet |
|
338 |
252 |
jshamlet |
signal IDX_Offset : ADDRESS_TYPE := x"0000";
|
339 |
|
|
|
340 |
|
|
signal IDX_Reg_l : integer := 0;
|
341 |
|
|
signal IDX_Reg_h : integer := 0;
|
342 |
|
|
|
343 |
|
|
signal IDX_NoOffset_Calc : ADDRESS_TYPE := x"0000";
|
344 |
|
|
signal IDX_Offset_Calc : ADDRESS_TYPE := x"0000";
|
345 |
|
|
|
346 |
169 |
jshamlet |
begin
|
347 |
|
|
|
348 |
224 |
jshamlet |
-------------------------------------------------------------------------------
|
349 |
|
|
-- Reset & uSec Tick
|
350 |
|
|
-------------------------------------------------------------------------------
|
351 |
185 |
jshamlet |
|
352 |
224 |
jshamlet |
CPU_Reset_Sync: process( Clock, PLL_Locked )
|
353 |
|
|
begin
|
354 |
|
|
if( PLL_Locked = '0' )then
|
355 |
|
|
Reset_q <= Reset_Level;
|
356 |
|
|
Reset <= Reset_Level;
|
357 |
|
|
elsif( rising_edge(Clock) )then
|
358 |
|
|
Reset_q <= not Reset_Level;
|
359 |
|
|
Reset <= Reset_q;
|
360 |
|
|
end if;
|
361 |
|
|
end process;
|
362 |
|
|
|
363 |
|
|
uSec_Tick_proc: process( Clock, Reset )
|
364 |
|
|
begin
|
365 |
|
|
if( Reset = Reset_Level )then
|
366 |
|
|
uSec_Cntr <= USEC_DLY;
|
367 |
|
|
uSec_Tick <= '0';
|
368 |
|
|
elsif( rising_edge( Clock ) )then
|
369 |
|
|
uSec_Cntr <= uSec_Cntr - 1;
|
370 |
|
|
if( or_reduce(uSec_Cntr) = '0' )then
|
371 |
|
|
uSec_Cntr <= USEC_DLY;
|
372 |
|
|
end if;
|
373 |
|
|
uSec_Tick <= nor_reduce(uSec_Cntr);
|
374 |
|
|
end if;
|
375 |
|
|
end process;
|
376 |
|
|
|
377 |
|
|
Open8_Bus.Clock <= Clock;
|
378 |
|
|
Open8_Bus.Reset <= Reset;
|
379 |
|
|
Open8_Bus.uSec_Tick <= uSec_Tick;
|
380 |
|
|
|
381 |
169 |
jshamlet |
-------------------------------------------------------------------------------
|
382 |
182 |
jshamlet |
-- Address bus selection/generation logic
|
383 |
169 |
jshamlet |
-------------------------------------------------------------------------------
|
384 |
|
|
|
385 |
252 |
jshamlet |
-- The original model treated the offset to LDO/STO as a signed value
|
386 |
|
|
-- allowing access to locations -128 to +127 from [Rn+1:Rn]. This isn't
|
387 |
|
|
-- always helpful, so the generic allows the CPU to use unsigned math
|
388 |
|
|
-- for the offsets. This makes the range 0 to +255 instead.
|
389 |
253 |
jshamlet |
|
390 |
252 |
jshamlet |
Unsigned_Idx_Offsets : if( Unsigned_Index_Offsets )generate
|
391 |
|
|
IDX_Offset(15 downto 8) <= (others => '0');
|
392 |
|
|
IDX_Offset(7 downto 0) <= Operand1;
|
393 |
|
|
end generate;
|
394 |
|
|
|
395 |
|
|
Signed_Idx_Offsets: if( not Unsigned_Index_Offsets )generate
|
396 |
|
|
IDX_Offset(15 downto 8) <= (others => Operand1(7));
|
397 |
|
|
IDX_Offset(7 downto 0) <= Operand1;
|
398 |
|
|
end generate;
|
399 |
|
|
|
400 |
|
|
-- Enable_Auto_Increment uses the LSB to determine whether or not to
|
401 |
|
|
-- do the auto-increment, so we need to lock the LSB for each operand
|
402 |
|
|
-- if it is enabled. This forces [ODD:EVEN] pairing.
|
403 |
|
|
|
404 |
|
|
Auto_Incr_Set: if( Enable_Auto_Increment )generate
|
405 |
|
|
IDX_Reg_l <= conv_integer(SubOp(2 downto 1) & '0');
|
406 |
|
|
IDX_Reg_h <= conv_integer(SubOp(2 downto 1) & '1');
|
407 |
|
|
end generate;
|
408 |
|
|
|
409 |
|
|
Auto_Incr_Not_Set: if( not Enable_Auto_Increment )generate
|
410 |
|
|
IDX_Reg_l <= conv_integer(SubOp);
|
411 |
|
|
IDX_Reg_h <= conv_integer(SubOp_p1);
|
412 |
|
|
end generate;
|
413 |
|
|
|
414 |
|
|
-- Pipeline registers for the indexed and indexed with offset addresses.
|
415 |
|
|
Idx_Addr_Calc_proc: process( Clock, Reset )
|
416 |
169 |
jshamlet |
variable Reg, Reg_1 : integer range 0 to 7 := 0;
|
417 |
|
|
begin
|
418 |
252 |
jshamlet |
if( Reset = Reset_Level )then
|
419 |
|
|
IDX_NoOffset_Calc <= x"0000";
|
420 |
|
|
IDX_Offset_Calc <= x"0000";
|
421 |
|
|
elsif( rising_edge(Clock))then
|
422 |
|
|
IDX_NoOffset_Calc <= (Regfile(IDX_Reg_h) & Regfile(IDX_Reg_l));
|
423 |
|
|
IDX_Offset_Calc <= (Regfile(IDX_Reg_h) & Regfile(IDX_Reg_l)) +
|
424 |
|
|
IDX_Offset;
|
425 |
182 |
jshamlet |
end if;
|
426 |
252 |
jshamlet |
end process;
|
427 |
182 |
jshamlet |
|
428 |
252 |
jshamlet |
-- Address selection logic based on current CPU state. This is combinatorial,
|
429 |
|
|
-- as adding pipeline registration would add a clock cycle to every instr,
|
430 |
|
|
-- without really adding the Fmax to compensate.
|
431 |
|
|
Address_Logic: process(CPU_State, Operand1, Operand2, IDX_NoOffset_Calc,
|
432 |
|
|
IDX_Offset_Calc, ISR_Addr, Stack_Ptr, Program_Ctr )
|
433 |
|
|
begin
|
434 |
182 |
jshamlet |
case( CPU_State )is
|
435 |
|
|
|
436 |
|
|
when LDA_C2 | STA_C2 =>
|
437 |
223 |
jshamlet |
Open8_Bus.Address <= Operand2 & Operand1;
|
438 |
182 |
jshamlet |
|
439 |
|
|
when LDX_C1 | STX_C1 =>
|
440 |
252 |
jshamlet |
Open8_Bus.Address <= IDX_NoOffset_Calc;
|
441 |
182 |
jshamlet |
|
442 |
252 |
jshamlet |
when LDO_C2 | STO_C2 =>
|
443 |
|
|
Open8_Bus.Address <= IDX_Offset_Calc;
|
444 |
182 |
jshamlet |
|
445 |
|
|
when ISR_C1 | ISR_C2 =>
|
446 |
223 |
jshamlet |
Open8_Bus.Address <= ISR_Addr;
|
447 |
182 |
jshamlet |
|
448 |
|
|
when PSH_C1 | POP_C1 | ISR_C3 | JSR_C1 | JSR_C2 | RTS_C1 | RTS_C2 | RTS_C3 =>
|
449 |
223 |
jshamlet |
Open8_Bus.Address <= Stack_Ptr;
|
450 |
182 |
jshamlet |
|
451 |
|
|
when others =>
|
452 |
223 |
jshamlet |
Open8_Bus.Address <= Program_Ctr;
|
453 |
182 |
jshamlet |
|
454 |
|
|
end case;
|
455 |
|
|
end process;
|
456 |
|
|
|
457 |
|
|
-------------------------------------------------------------------------------
|
458 |
|
|
-- Combinatorial portion of CPU finite state machine
|
459 |
|
|
-- State Logic / Instruction Decoding & Execution
|
460 |
|
|
-------------------------------------------------------------------------------
|
461 |
|
|
|
462 |
187 |
jshamlet |
State_Logic: process(CPU_State, Flags, Int_Mask, CPU_Halt_Req, Opcode,
|
463 |
182 |
jshamlet |
SubOp , SubOp_p1, Operand1, Operand2, Int_Req )
|
464 |
|
|
variable Reg : integer range 0 to 7 := 0;
|
465 |
|
|
begin
|
466 |
169 |
jshamlet |
CPU_Next_State <= CPU_State;
|
467 |
|
|
Cache_Ctrl <= CACHE_IDLE;
|
468 |
|
|
--
|
469 |
185 |
jshamlet |
PC_Ctrl.Oper <= PC_INCR;
|
470 |
|
|
PC_Ctrl.Offset <= PC_IDLE;
|
471 |
182 |
jshamlet |
--
|
472 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_IDLE;
|
473 |
|
|
ALU_Ctrl.Reg <= ACCUM;
|
474 |
|
|
--
|
475 |
|
|
SP_Ctrl.Oper <= SP_IDLE;
|
476 |
|
|
--
|
477 |
|
|
DP_Ctrl.Src <= DATA_RD_MEM;
|
478 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
479 |
|
|
--
|
480 |
|
|
INT_Ctrl.Mask_Set <= '0';
|
481 |
|
|
INT_Ctrl.Soft_Ints <= x"00";
|
482 |
|
|
INT_Ctrl.Incr_ISR <= '0';
|
483 |
|
|
Ack_D <= '0';
|
484 |
225 |
jshamlet |
--
|
485 |
182 |
jshamlet |
Reg := conv_integer(SubOp);
|
486 |
225 |
jshamlet |
--
|
487 |
|
|
CPU_Halt_Ack <= '0';
|
488 |
169 |
jshamlet |
|
489 |
|
|
case CPU_State is
|
490 |
|
|
-------------------------------------------------------------------------------
|
491 |
|
|
-- Initial Instruction fetch & decode
|
492 |
|
|
-------------------------------------------------------------------------------
|
493 |
187 |
jshamlet |
when IPF_C0 =>
|
494 |
|
|
CPU_Next_State <= IPF_C1;
|
495 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
496 |
169 |
jshamlet |
|
497 |
187 |
jshamlet |
when IPF_C1 =>
|
498 |
|
|
CPU_Next_State <= IPF_C2;
|
499 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
500 |
169 |
jshamlet |
|
501 |
187 |
jshamlet |
when IPF_C2 =>
|
502 |
|
|
CPU_Next_State <= IDC_C0;
|
503 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
504 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
505 |
169 |
jshamlet |
|
506 |
187 |
jshamlet |
when IDC_C0 =>
|
507 |
|
|
CPU_Next_State <= IDC_C0;
|
508 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
509 |
|
|
|
510 |
|
|
case Opcode is
|
511 |
|
|
when OP_PSH =>
|
512 |
|
|
CPU_Next_State <= PSH_C1;
|
513 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
514 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV1;
|
515 |
169 |
jshamlet |
DP_Ctrl.Src <= DATA_WR_REG;
|
516 |
|
|
DP_Ctrl.Reg <= SubOp;
|
517 |
|
|
|
518 |
|
|
when OP_POP =>
|
519 |
|
|
CPU_Next_State <= POP_C1;
|
520 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
521 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV2;
|
522 |
169 |
jshamlet |
SP_Ctrl.Oper <= SP_POP;
|
523 |
|
|
|
524 |
|
|
when OP_BR0 | OP_BR1 =>
|
525 |
|
|
CPU_Next_State <= BRN_C1;
|
526 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
527 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
528 |
169 |
jshamlet |
|
529 |
185 |
jshamlet |
|
530 |
169 |
jshamlet |
when OP_DBNZ =>
|
531 |
|
|
CPU_Next_State <= DBNZ_C1;
|
532 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
533 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
534 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_DEC;
|
535 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
536 |
|
|
|
537 |
|
|
when OP_INT =>
|
538 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
539 |
187 |
jshamlet |
-- Make sure the requested interrupt is actually enabled first.
|
540 |
|
|
-- Also, unlike CPU_Halt, the INT instruction is actually being
|
541 |
|
|
-- executed, so go ahead and increment the program counter before
|
542 |
|
|
-- pausing so the CPU restarts on the next instruction.
|
543 |
169 |
jshamlet |
if( Int_Mask(Reg) = '1' )then
|
544 |
187 |
jshamlet |
CPU_Next_State <= WAI_Cx;
|
545 |
169 |
jshamlet |
INT_Ctrl.Soft_Ints(Reg) <= '1';
|
546 |
|
|
end if;
|
547 |
|
|
|
548 |
|
|
when OP_STK =>
|
549 |
|
|
case SubOp is
|
550 |
|
|
when SOP_RSP =>
|
551 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
552 |
181 |
jshamlet |
if( not Allow_Stack_Address_Move )then
|
553 |
187 |
jshamlet |
-- The default behavior for this instruction is to simply
|
554 |
|
|
-- repoint the SP to the HDL default
|
555 |
185 |
jshamlet |
SP_Ctrl.Oper <= SP_CLR;
|
556 |
181 |
jshamlet |
end if;
|
557 |
187 |
jshamlet |
if( Allow_Stack_Address_Move and
|
558 |
|
|
Flags(Stack_Xfer_Flag) = '1' )then
|
559 |
|
|
-- If RSP is set to allow SP moves, and the specified flag
|
560 |
|
|
-- is true, then signal the stack pointer logic to load
|
561 |
|
|
-- from R1:R0
|
562 |
185 |
jshamlet |
SP_Ctrl.Oper <= SP_SET;
|
563 |
181 |
jshamlet |
end if;
|
564 |
187 |
jshamlet |
if( Allow_Stack_Address_Move and
|
565 |
|
|
Flags(Stack_Xfer_Flag) = '0')then
|
566 |
|
|
-- If RSP is set to allow SP moves, and the specified flag
|
567 |
|
|
-- is false, then signal the ALU to copy the stack pointer
|
568 |
|
|
-- to R1:R0
|
569 |
185 |
jshamlet |
ALU_Ctrl.Oper <= ALU_RSP;
|
570 |
181 |
jshamlet |
end if;
|
571 |
169 |
jshamlet |
|
572 |
|
|
when SOP_RTS | SOP_RTI =>
|
573 |
185 |
jshamlet |
CPU_Next_State <= RTS_C1;
|
574 |
190 |
jshamlet |
Cache_Ctrl <= CACHE_IDLE;
|
575 |
185 |
jshamlet |
SP_Ctrl.Oper <= SP_POP;
|
576 |
169 |
jshamlet |
|
577 |
|
|
when SOP_BRK =>
|
578 |
|
|
if( BRK_Implements_WAI )then
|
579 |
187 |
jshamlet |
-- If BRK_Implements_WAI, then jump to the WAI_Cx and
|
580 |
|
|
-- increment the PC similar to an ISR flow.
|
581 |
|
|
CPU_Next_State <= WAI_Cx;
|
582 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
583 |
187 |
jshamlet |
else
|
584 |
|
|
-- If Break is implemented normally, back the PC up by
|
585 |
|
|
-- 2 and return through IPF_C0 in order to execute a 5
|
586 |
|
|
-- clock cycle delay
|
587 |
|
|
CPU_Next_State <= BRK_C1;
|
588 |
|
|
PC_Ctrl.Offset <= PC_REV2;
|
589 |
169 |
jshamlet |
end if;
|
590 |
|
|
|
591 |
|
|
when SOP_JMP =>
|
592 |
185 |
jshamlet |
CPU_Next_State <= JMP_C1;
|
593 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
594 |
169 |
jshamlet |
|
595 |
|
|
when SOP_SMSK =>
|
596 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
597 |
169 |
jshamlet |
INT_Ctrl.Mask_Set <= '1';
|
598 |
|
|
|
599 |
|
|
when SOP_GMSK =>
|
600 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
601 |
|
|
ALU_Ctrl.Oper <= ALU_GMSK;
|
602 |
169 |
jshamlet |
|
603 |
|
|
when SOP_JSR =>
|
604 |
|
|
CPU_Next_State <= JSR_C1;
|
605 |
185 |
jshamlet |
Cache_Ctrl <= CACHE_OPER1;
|
606 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
607 |
|
|
DP_Ctrl.Reg <= PC_MSB;
|
608 |
169 |
jshamlet |
|
609 |
|
|
when others => null;
|
610 |
|
|
end case;
|
611 |
|
|
|
612 |
|
|
when OP_MUL =>
|
613 |
|
|
CPU_Next_State <= MUL_C1;
|
614 |
181 |
jshamlet |
-- Multiplication requires a single clock cycle to calculate PRIOR
|
615 |
|
|
-- to the ALU writing the result to registers. As a result, this
|
616 |
|
|
-- state needs to idle the ALU initially, and back the PC up by 1
|
617 |
|
|
-- We can get away with only 1 extra clock by pre-fetching the
|
618 |
|
|
-- next instruction, though.
|
619 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_PREFETCH;
|
620 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV1;
|
621 |
181 |
jshamlet |
-- Note that both the multiply process AND ALU process need the
|
622 |
|
|
-- source register for Rn (R1:R0 = R0 * Rn). Assert ALU_Ctrl.reg
|
623 |
|
|
-- now, but hold off on the ALU command until the next state.
|
624 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_IDLE;
|
625 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
626 |
|
|
|
627 |
|
|
when OP_UPP =>
|
628 |
|
|
CPU_Next_State <= UPP_C1;
|
629 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
630 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV1;
|
631 |
169 |
jshamlet |
ALU_Ctrl.Oper <= Opcode;
|
632 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
633 |
|
|
|
634 |
|
|
when OP_LDA =>
|
635 |
|
|
CPU_Next_State <= LDA_C1;
|
636 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
637 |
|
|
|
638 |
|
|
when OP_LDI =>
|
639 |
|
|
CPU_Next_State <= LDI_C1;
|
640 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
641 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
642 |
169 |
jshamlet |
|
643 |
|
|
when OP_LDO =>
|
644 |
|
|
CPU_Next_State <= LDO_C1;
|
645 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
646 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV2;
|
647 |
169 |
jshamlet |
|
648 |
|
|
when OP_LDX =>
|
649 |
|
|
CPU_Next_State <= LDX_C1;
|
650 |
181 |
jshamlet |
Cache_Ctrl <= CACHE_PREFETCH;
|
651 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV2;
|
652 |
169 |
jshamlet |
|
653 |
|
|
when OP_STA =>
|
654 |
|
|
CPU_Next_State <= STA_C1;
|
655 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
656 |
|
|
|
657 |
|
|
when OP_STO =>
|
658 |
|
|
CPU_Next_State <= STO_C1;
|
659 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
660 |
252 |
jshamlet |
PC_Ctrl.Offset <= PC_REV1;
|
661 |
169 |
jshamlet |
|
662 |
|
|
when OP_STX =>
|
663 |
|
|
CPU_Next_State <= STX_C1;
|
664 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
665 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_REV2;
|
666 |
169 |
jshamlet |
DP_Ctrl.Src <= DATA_WR_REG;
|
667 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
668 |
|
|
|
669 |
244 |
jshamlet |
when OP_STP =>
|
670 |
|
|
PC_Ctrl.Offset <= PC_NEXT;
|
671 |
|
|
if( Supervisor_Mode )then
|
672 |
|
|
if( SubOp /= PSR_I )then
|
673 |
|
|
ALU_Ctrl.Oper <= Opcode;
|
674 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
675 |
|
|
end if;
|
676 |
|
|
else
|
677 |
|
|
ALU_Ctrl.Oper <= Opcode;
|
678 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
679 |
|
|
end if;
|
680 |
|
|
|
681 |
169 |
jshamlet |
when others =>
|
682 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
683 |
169 |
jshamlet |
ALU_Ctrl.Oper <= Opcode;
|
684 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
685 |
|
|
|
686 |
|
|
end case;
|
687 |
|
|
|
688 |
186 |
jshamlet |
if( Int_Req = '1' )then
|
689 |
|
|
CPU_Next_State <= ISR_C1;
|
690 |
187 |
jshamlet |
end if;
|
691 |
|
|
|
692 |
|
|
if( CPU_Halt_Req = '1' )then
|
693 |
|
|
CPU_Next_State <= WAH_Cx;
|
694 |
|
|
end if;
|
695 |
|
|
|
696 |
|
|
-- If either of these override conditions are true, the decoder needs
|
697 |
|
|
-- to undo everything it just setup, since even "single-cycle"
|
698 |
|
|
-- instructions will be executed again upon return.
|
699 |
|
|
if( Int_Req = '1' or CPU_Halt_Req = '1' )then
|
700 |
|
|
-- In either case, we want to skip loading the cache, as the cache
|
701 |
|
|
-- will be invalid by the time we get back.
|
702 |
186 |
jshamlet |
Cache_Ctrl <= CACHE_IDLE;
|
703 |
187 |
jshamlet |
-- Rewind the PC by 3 to put the PC back to the current instruction,
|
704 |
|
|
-- compensating for the pipeline registers.
|
705 |
186 |
jshamlet |
PC_Ctrl.Offset <= PC_REV3;
|
706 |
|
|
-- Reset all of the sub-block controls to IDLE, to avoid unintended
|
707 |
187 |
jshamlet |
-- operation due to the current instruction.
|
708 |
186 |
jshamlet |
ALU_Ctrl.Oper <= ALU_IDLE;
|
709 |
|
|
SP_Ctrl.Oper <= SP_IDLE;
|
710 |
187 |
jshamlet |
-- Interrupt logic outside of the state machine needs this to be set
|
711 |
|
|
-- to DATA_RD_MEM, while CPU_Halt considers this a "don't care".
|
712 |
186 |
jshamlet |
DP_Ctrl.Src <= DATA_RD_MEM;
|
713 |
187 |
jshamlet |
-- If an INT/SMSK instruction was going to be executed, it will get
|
714 |
|
|
-- executed again when normal processing resumes, so axe their
|
715 |
|
|
-- requests for now.
|
716 |
|
|
INT_Ctrl.Mask_Set <= '0';
|
717 |
|
|
INT_Ctrl.Soft_Ints(Reg) <= '0';
|
718 |
186 |
jshamlet |
end if;
|
719 |
|
|
|
720 |
169 |
jshamlet |
-------------------------------------------------------------------------------
|
721 |
|
|
-- Program Control (BR0_C1, BR1_C1, DBNZ_C1, JMP )
|
722 |
|
|
-------------------------------------------------------------------------------
|
723 |
|
|
|
724 |
|
|
when BRN_C1 =>
|
725 |
187 |
jshamlet |
CPU_Next_State <= IDC_C0;
|
726 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
727 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
728 |
169 |
jshamlet |
if( Flags(Reg) = Opcode(0) )then
|
729 |
187 |
jshamlet |
CPU_Next_State <= IPF_C0;
|
730 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_IDLE;
|
731 |
|
|
PC_Ctrl.Offset <= Operand1;
|
732 |
|
|
end if;
|
733 |
|
|
|
734 |
|
|
when DBNZ_C1 =>
|
735 |
187 |
jshamlet |
CPU_Next_State <= IDC_C0;
|
736 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
737 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
738 |
|
|
if( Flags(PSR_Z) = '0' )then
|
739 |
187 |
jshamlet |
CPU_Next_State <= IPF_C0;
|
740 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_IDLE;
|
741 |
|
|
PC_Ctrl.Offset <= Operand1;
|
742 |
|
|
end if;
|
743 |
|
|
|
744 |
|
|
when JMP_C1 =>
|
745 |
|
|
CPU_Next_State <= JMP_C2;
|
746 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
747 |
|
|
|
748 |
|
|
when JMP_C2 =>
|
749 |
187 |
jshamlet |
CPU_Next_State <= IPF_C0;
|
750 |
169 |
jshamlet |
PC_Ctrl.Oper <= PC_LOAD;
|
751 |
|
|
|
752 |
|
|
-------------------------------------------------------------------------------
|
753 |
|
|
-- Data Storage - Load from memory (LDA, LDI, LDO, LDX)
|
754 |
|
|
-------------------------------------------------------------------------------
|
755 |
|
|
|
756 |
|
|
when LDA_C1 =>
|
757 |
|
|
CPU_Next_State <= LDA_C2;
|
758 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
759 |
|
|
|
760 |
|
|
when LDA_C2 =>
|
761 |
|
|
CPU_Next_State <= LDA_C3;
|
762 |
|
|
|
763 |
|
|
when LDA_C3 =>
|
764 |
|
|
CPU_Next_State <= LDA_C4;
|
765 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
766 |
169 |
jshamlet |
|
767 |
|
|
when LDA_C4 =>
|
768 |
|
|
CPU_Next_State <= LDI_C1;
|
769 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
770 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
771 |
169 |
jshamlet |
|
772 |
|
|
when LDI_C1 =>
|
773 |
187 |
jshamlet |
CPU_Next_State <= IDC_C0;
|
774 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
775 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
776 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_LDI;
|
777 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
778 |
|
|
|
779 |
|
|
when LDO_C1 =>
|
780 |
252 |
jshamlet |
CPU_Next_State <= LDO_C2;
|
781 |
|
|
|
782 |
|
|
when LDO_C2 =>
|
783 |
181 |
jshamlet |
CPU_Next_State <= LDX_C2;
|
784 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
785 |
182 |
jshamlet |
if( Enable_Auto_Increment and SubOp(0) = '1' )then
|
786 |
|
|
ALU_Ctrl.Oper <= ALU_UPP;
|
787 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
788 |
169 |
jshamlet |
end if;
|
789 |
|
|
|
790 |
|
|
when LDX_C1 =>
|
791 |
|
|
CPU_Next_State <= LDX_C2;
|
792 |
182 |
jshamlet |
if( Enable_Auto_Increment and SubOp(0) = '1' )then
|
793 |
|
|
ALU_Ctrl.Oper <= ALU_UPP;
|
794 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
795 |
181 |
jshamlet |
end if;
|
796 |
169 |
jshamlet |
|
797 |
|
|
when LDX_C2 =>
|
798 |
|
|
CPU_Next_State <= LDX_C3;
|
799 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
800 |
181 |
jshamlet |
|
801 |
|
|
when LDX_C3 =>
|
802 |
|
|
CPU_Next_State <= LDX_C4;
|
803 |
182 |
jshamlet |
Cache_Ctrl <= CACHE_OPER1;
|
804 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
805 |
169 |
jshamlet |
|
806 |
181 |
jshamlet |
when LDX_C4 =>
|
807 |
187 |
jshamlet |
CPU_Next_State <= IDC_C0;
|
808 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
809 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
810 |
181 |
jshamlet |
ALU_Ctrl.Oper <= ALU_LDI;
|
811 |
169 |
jshamlet |
ALU_Ctrl.Reg <= ACCUM;
|
812 |
|
|
|
813 |
|
|
-------------------------------------------------------------------------------
|
814 |
|
|
-- Data Storage - Store to memory (STA, STO, STX)
|
815 |
|
|
-------------------------------------------------------------------------------
|
816 |
|
|
when STA_C1 =>
|
817 |
|
|
CPU_Next_State <= STA_C2;
|
818 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
819 |
|
|
DP_Ctrl.Src <= DATA_WR_REG;
|
820 |
|
|
DP_Ctrl.Reg <= SubOp;
|
821 |
|
|
|
822 |
|
|
when STA_C2 =>
|
823 |
|
|
CPU_Next_State <= STA_C3;
|
824 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
825 |
169 |
jshamlet |
|
826 |
|
|
when STA_C3 =>
|
827 |
187 |
jshamlet |
CPU_Next_State <= IPF_C2;
|
828 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_PREFETCH;
|
829 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
830 |
169 |
jshamlet |
|
831 |
|
|
when STO_C1 =>
|
832 |
252 |
jshamlet |
CPU_Next_State <= STO_C2;
|
833 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_PREFETCH;
|
834 |
252 |
jshamlet |
DP_Ctrl.Src <= DATA_WR_REG;
|
835 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
836 |
|
|
|
837 |
|
|
when STO_C2 =>
|
838 |
|
|
CPU_Next_State <= IPF_C1;
|
839 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
840 |
182 |
jshamlet |
if( Enable_Auto_Increment and SubOp(0) = '1' )then
|
841 |
252 |
jshamlet |
CPU_Next_State <= STO_C3;
|
842 |
182 |
jshamlet |
ALU_Ctrl.Oper <= ALU_UPP;
|
843 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
844 |
169 |
jshamlet |
end if;
|
845 |
|
|
|
846 |
252 |
jshamlet |
when STO_C3 =>
|
847 |
|
|
CPU_Next_State <= IPF_C2;
|
848 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
849 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_UPP2;
|
850 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '1';
|
851 |
|
|
|
852 |
|
|
when STX_C1 =>
|
853 |
187 |
jshamlet |
CPU_Next_State <= IPF_C1;
|
854 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
855 |
182 |
jshamlet |
if( Enable_Auto_Increment and SubOp(0) = '1' )then
|
856 |
|
|
CPU_Next_State <= STX_C2;
|
857 |
|
|
ALU_Ctrl.Oper <= ALU_UPP;
|
858 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
859 |
169 |
jshamlet |
end if;
|
860 |
|
|
|
861 |
|
|
when STX_C2 =>
|
862 |
187 |
jshamlet |
CPU_Next_State <= IPF_C2;
|
863 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
864 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_UPP2;
|
865 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '1';
|
866 |
|
|
|
867 |
|
|
-------------------------------------------------------------------------------
|
868 |
|
|
-- Multi-Cycle Math Operations (UPP, MUL)
|
869 |
|
|
-------------------------------------------------------------------------------
|
870 |
|
|
|
871 |
|
|
-- Because we have to backup the pipeline by 1 to refetch the 2nd
|
872 |
181 |
jshamlet |
-- instruction/first operand, we have to return through PF2. Also, we
|
873 |
|
|
-- need to tell the ALU to store the results to R1:R0 here. Note that
|
874 |
|
|
-- there is no ALU_Ctrl.Reg, as this is implied in the ALU instruction
|
875 |
169 |
jshamlet |
when MUL_C1 =>
|
876 |
187 |
jshamlet |
CPU_Next_State <= IPF_C2;
|
877 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
878 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_MUL;
|
879 |
|
|
|
880 |
|
|
when UPP_C1 =>
|
881 |
187 |
jshamlet |
CPU_Next_State <= IPF_C2;
|
882 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
883 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_UPP2;
|
884 |
|
|
ALU_Ctrl.Reg <= SubOp_p1;
|
885 |
|
|
|
886 |
|
|
-------------------------------------------------------------------------------
|
887 |
|
|
-- Basic Stack Manipulation (PSH, POP, RSP)
|
888 |
|
|
-------------------------------------------------------------------------------
|
889 |
|
|
when PSH_C1 =>
|
890 |
187 |
jshamlet |
CPU_Next_State <= IPF_C1;
|
891 |
169 |
jshamlet |
SP_Ctrl.Oper <= SP_PUSH;
|
892 |
|
|
|
893 |
|
|
when POP_C1 =>
|
894 |
|
|
CPU_Next_State <= POP_C2;
|
895 |
|
|
|
896 |
|
|
when POP_C2 =>
|
897 |
|
|
CPU_Next_State <= POP_C3;
|
898 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
899 |
169 |
jshamlet |
|
900 |
|
|
when POP_C3 =>
|
901 |
|
|
CPU_Next_State <= POP_C4;
|
902 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
903 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
904 |
169 |
jshamlet |
|
905 |
|
|
when POP_C4 =>
|
906 |
187 |
jshamlet |
CPU_Next_State <= IDC_C0;
|
907 |
169 |
jshamlet |
Cache_Ctrl <= CACHE_INSTR;
|
908 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
909 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_POP;
|
910 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
911 |
172 |
jshamlet |
|
912 |
169 |
jshamlet |
-------------------------------------------------------------------------------
|
913 |
|
|
-- Subroutines & Interrupts (RTS, JSR)
|
914 |
|
|
-------------------------------------------------------------------------------
|
915 |
187 |
jshamlet |
when WAI_Cx => -- For soft interrupts only, halt the Program_Ctr
|
916 |
169 |
jshamlet |
DP_Ctrl.Src <= DATA_BUS_IDLE;
|
917 |
186 |
jshamlet |
if( Int_Req = '1' )then
|
918 |
|
|
CPU_Next_State <= ISR_C1;
|
919 |
187 |
jshamlet |
-- Rewind the PC by 3 to put the PC back to would have been the next
|
920 |
|
|
-- instruction, compensating for the pipeline registers.
|
921 |
186 |
jshamlet |
PC_Ctrl.Offset <= PC_REV3;
|
922 |
|
|
-- Reset all of the sub-block controls to IDLE, to avoid unintended
|
923 |
|
|
-- operation due to the current instruction
|
924 |
|
|
DP_Ctrl.Src <= DATA_RD_MEM;
|
925 |
|
|
end if;
|
926 |
169 |
jshamlet |
|
927 |
187 |
jshamlet |
when WAH_Cx => -- Holds until CPU_Halt_Req is deasserted.
|
928 |
225 |
jshamlet |
CPU_Halt_Ack <= '1';
|
929 |
187 |
jshamlet |
DP_Ctrl.Src <= DATA_BUS_IDLE;
|
930 |
|
|
if( CPU_Halt_Req = '0' )then
|
931 |
|
|
CPU_Next_State <= IPF_C0;
|
932 |
|
|
DP_Ctrl.Src <= DATA_RD_MEM;
|
933 |
|
|
end if;
|
934 |
|
|
|
935 |
|
|
when BRK_C1 => -- Debugging (BRK) Performs a 5-clock NOP.
|
936 |
|
|
CPU_Next_State <= IPF_C0;
|
937 |
|
|
|
938 |
169 |
jshamlet |
when ISR_C1 =>
|
939 |
|
|
CPU_Next_State <= ISR_C2;
|
940 |
|
|
INT_Ctrl.Incr_ISR <= '1';
|
941 |
|
|
|
942 |
|
|
when ISR_C2 =>
|
943 |
|
|
CPU_Next_State <= ISR_C3;
|
944 |
|
|
DP_Ctrl.Src <= DATA_WR_FLAG;
|
945 |
|
|
|
946 |
|
|
when ISR_C3 =>
|
947 |
|
|
CPU_Next_State <= JSR_C1;
|
948 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
949 |
182 |
jshamlet |
ALU_Ctrl.Oper <= ALU_STP;
|
950 |
185 |
jshamlet |
ALU_Ctrl.Reg <= conv_std_logic_vector(PSR_I,3);
|
951 |
169 |
jshamlet |
SP_Ctrl.Oper <= SP_PUSH;
|
952 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
953 |
182 |
jshamlet |
DP_Ctrl.Reg <= PC_MSB;
|
954 |
169 |
jshamlet |
Ack_D <= '1';
|
955 |
|
|
|
956 |
|
|
when JSR_C1 =>
|
957 |
|
|
CPU_Next_State <= JSR_C2;
|
958 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
959 |
|
|
SP_Ctrl.Oper <= SP_PUSH;
|
960 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
961 |
182 |
jshamlet |
DP_Ctrl.Reg <= PC_LSB;
|
962 |
169 |
jshamlet |
|
963 |
|
|
when JSR_C2 =>
|
964 |
187 |
jshamlet |
CPU_Next_State <= IPF_C0;
|
965 |
169 |
jshamlet |
PC_Ctrl.Oper <= PC_LOAD;
|
966 |
182 |
jshamlet |
SP_Ctrl.Oper <= SP_PUSH;
|
967 |
169 |
jshamlet |
|
968 |
|
|
when RTS_C1 =>
|
969 |
|
|
CPU_Next_State <= RTS_C2;
|
970 |
|
|
SP_Ctrl.Oper <= SP_POP;
|
971 |
|
|
|
972 |
|
|
when RTS_C2 =>
|
973 |
|
|
CPU_Next_State <= RTS_C3;
|
974 |
|
|
-- if this is an RTI, then we need to POP the flags
|
975 |
|
|
if( SubOp = SOP_RTI )then
|
976 |
|
|
SP_Ctrl.Oper <= SP_POP;
|
977 |
|
|
end if;
|
978 |
|
|
|
979 |
|
|
when RTS_C3 =>
|
980 |
|
|
CPU_Next_State <= RTS_C4;
|
981 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
982 |
|
|
|
983 |
|
|
when RTS_C4 =>
|
984 |
|
|
CPU_Next_State <= RTS_C5;
|
985 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
986 |
|
|
|
987 |
|
|
when RTS_C5 =>
|
988 |
187 |
jshamlet |
CPU_Next_State <= IPF_C0;
|
989 |
169 |
jshamlet |
PC_Ctrl.Oper <= PC_LOAD;
|
990 |
185 |
jshamlet |
-- if this is an RTI, then we need to clear the I bit
|
991 |
169 |
jshamlet |
if( SubOp = SOP_RTI )then
|
992 |
|
|
CPU_Next_State <= RTI_C6;
|
993 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
994 |
185 |
jshamlet |
ALU_Ctrl.Oper <= ALU_CLP;
|
995 |
|
|
ALU_Ctrl.Reg <= conv_std_logic_vector(PSR_I,3);
|
996 |
169 |
jshamlet |
end if;
|
997 |
|
|
|
998 |
|
|
when RTI_C6 =>
|
999 |
187 |
jshamlet |
CPU_Next_State <= IPF_C1;
|
1000 |
185 |
jshamlet |
PC_Ctrl.Offset <= PC_NEXT;
|
1001 |
169 |
jshamlet |
ALU_Ctrl.Oper <= ALU_RFLG;
|
1002 |
|
|
|
1003 |
|
|
when others =>
|
1004 |
|
|
null;
|
1005 |
|
|
end case;
|
1006 |
|
|
|
1007 |
|
|
end process;
|
1008 |
|
|
|
1009 |
|
|
-------------------------------------------------------------------------------
|
1010 |
|
|
-- Registered portion of CPU finite state machine
|
1011 |
|
|
-------------------------------------------------------------------------------
|
1012 |
182 |
jshamlet |
|
1013 |
169 |
jshamlet |
CPU_Regs: process( Reset, Clock )
|
1014 |
|
|
variable Offset_SX : ADDRESS_TYPE;
|
1015 |
188 |
jshamlet |
variable i_Ints : INTERRUPT_BUNDLE := x"00";
|
1016 |
169 |
jshamlet |
variable Index : integer range 0 to 7 := 0;
|
1017 |
|
|
variable Sum : std_logic_vector(8 downto 0) := "000000000";
|
1018 |
|
|
variable Temp : std_logic_vector(8 downto 0) := "000000000";
|
1019 |
|
|
begin
|
1020 |
|
|
if( Reset = Reset_Level )then
|
1021 |
187 |
jshamlet |
CPU_State <= IPF_C0;
|
1022 |
169 |
jshamlet |
Opcode <= OP_INC;
|
1023 |
|
|
SubOp <= ACCUM;
|
1024 |
|
|
SubOp_p1 <= ACCUM;
|
1025 |
|
|
Operand1 <= x"00";
|
1026 |
|
|
Operand2 <= x"00";
|
1027 |
|
|
Instr_Prefetch <= '0';
|
1028 |
|
|
Prefetch <= x"00";
|
1029 |
|
|
|
1030 |
187 |
jshamlet |
CPU_Halt_Req <= '0';
|
1031 |
225 |
jshamlet |
Halt_Ack <= '0';
|
1032 |
187 |
jshamlet |
|
1033 |
223 |
jshamlet |
Open8_Bus.Wr_En <= '0';
|
1034 |
|
|
Open8_Bus.Wr_Data <= OPEN8_NULLBUS;
|
1035 |
|
|
Open8_Bus.Rd_En <= '1';
|
1036 |
169 |
jshamlet |
|
1037 |
|
|
Program_Ctr <= Program_Start_Addr;
|
1038 |
|
|
Stack_Ptr <= Stack_Start_Addr;
|
1039 |
|
|
|
1040 |
|
|
Ack_Q <= '0';
|
1041 |
|
|
Ack_Q1 <= '0';
|
1042 |
|
|
Int_Ack <= '0';
|
1043 |
|
|
|
1044 |
|
|
Int_Req <= '0';
|
1045 |
|
|
Pending <= x"00";
|
1046 |
|
|
Wait_for_FSM <= '0';
|
1047 |
210 |
jshamlet |
Wait_for_ISR <= '0';
|
1048 |
245 |
jshamlet |
Set_Mask <= '0';
|
1049 |
169 |
jshamlet |
if( Enable_NMI )then
|
1050 |
|
|
Int_Mask <= Default_Interrupt_Mask(7 downto 1) & '1';
|
1051 |
|
|
else
|
1052 |
|
|
Int_Mask <= Default_Interrupt_Mask;
|
1053 |
|
|
end if;
|
1054 |
|
|
ISR_Addr <= INT_VECTOR_0;
|
1055 |
|
|
|
1056 |
|
|
for i in 0 to 7 loop
|
1057 |
188 |
jshamlet |
Regfile(i) <= x"00";
|
1058 |
169 |
jshamlet |
end loop;
|
1059 |
|
|
Flags <= x"00";
|
1060 |
248 |
jshamlet |
if( Supervisor_Mode )then
|
1061 |
244 |
jshamlet |
Flags(PSR_I) <= '1';
|
1062 |
|
|
end if;
|
1063 |
169 |
jshamlet |
|
1064 |
224 |
jshamlet |
Open8_Bus.GP_Flags <= (others => '0');
|
1065 |
188 |
jshamlet |
|
1066 |
169 |
jshamlet |
elsif( rising_edge(Clock) )then
|
1067 |
187 |
jshamlet |
|
1068 |
225 |
jshamlet |
CPU_Halt_Req <= Halt_Req;
|
1069 |
|
|
Halt_Ack <= CPU_Halt_Ack;
|
1070 |
187 |
jshamlet |
|
1071 |
223 |
jshamlet |
Open8_Bus.Wr_En <= '0';
|
1072 |
|
|
Open8_Bus.Wr_Data <= OPEN8_NULLBUS;
|
1073 |
|
|
Open8_Bus.Rd_En <= '0';
|
1074 |
169 |
jshamlet |
|
1075 |
|
|
-------------------------------------------------------------------------------
|
1076 |
|
|
-- Instruction/Operand caching for pipelined memory access
|
1077 |
|
|
-------------------------------------------------------------------------------
|
1078 |
|
|
CPU_State <= CPU_Next_State;
|
1079 |
|
|
case Cache_Ctrl is
|
1080 |
|
|
when CACHE_INSTR =>
|
1081 |
|
|
Opcode <= Rd_Data(7 downto 3);
|
1082 |
|
|
SubOp <= Rd_Data(2 downto 0);
|
1083 |
|
|
SubOp_p1 <= Rd_Data(2 downto 0) + 1;
|
1084 |
|
|
if( Instr_Prefetch = '1' )then
|
1085 |
|
|
Opcode <= Prefetch(7 downto 3);
|
1086 |
|
|
SubOp <= Prefetch(2 downto 0);
|
1087 |
|
|
SubOp_p1 <= Prefetch(2 downto 0) + 1;
|
1088 |
|
|
Instr_Prefetch <= '0';
|
1089 |
|
|
end if;
|
1090 |
|
|
|
1091 |
|
|
when CACHE_OPER1 =>
|
1092 |
|
|
Operand1 <= Rd_Data;
|
1093 |
|
|
|
1094 |
|
|
when CACHE_OPER2 =>
|
1095 |
|
|
Operand2 <= Rd_Data;
|
1096 |
|
|
|
1097 |
|
|
when CACHE_PREFETCH =>
|
1098 |
|
|
Prefetch <= Rd_Data;
|
1099 |
|
|
Instr_Prefetch <= '1';
|
1100 |
|
|
|
1101 |
|
|
when CACHE_IDLE =>
|
1102 |
|
|
null;
|
1103 |
|
|
end case;
|
1104 |
|
|
|
1105 |
|
|
-------------------------------------------------------------------------------
|
1106 |
|
|
-- Program Counter
|
1107 |
|
|
-------------------------------------------------------------------------------
|
1108 |
|
|
Offset_SX(15 downto 8) := (others => PC_Ctrl.Offset(7));
|
1109 |
|
|
Offset_SX(7 downto 0) := PC_Ctrl.Offset;
|
1110 |
|
|
|
1111 |
|
|
case PC_Ctrl.Oper is
|
1112 |
|
|
when PC_INCR =>
|
1113 |
|
|
Program_Ctr <= Program_Ctr + Offset_SX - 2;
|
1114 |
|
|
|
1115 |
|
|
when PC_LOAD =>
|
1116 |
185 |
jshamlet |
Program_Ctr <= Operand2 & Operand1;
|
1117 |
169 |
jshamlet |
|
1118 |
|
|
when others =>
|
1119 |
|
|
null;
|
1120 |
|
|
end case;
|
1121 |
|
|
|
1122 |
|
|
-------------------------------------------------------------------------------
|
1123 |
|
|
-- (Write) Data Path
|
1124 |
|
|
-------------------------------------------------------------------------------
|
1125 |
|
|
case DP_Ctrl.Src is
|
1126 |
|
|
when DATA_BUS_IDLE =>
|
1127 |
|
|
null;
|
1128 |
|
|
|
1129 |
|
|
when DATA_RD_MEM =>
|
1130 |
223 |
jshamlet |
Open8_Bus.Rd_En <= '1';
|
1131 |
169 |
jshamlet |
|
1132 |
|
|
when DATA_WR_REG =>
|
1133 |
223 |
jshamlet |
Open8_Bus.Wr_En <= '1';
|
1134 |
|
|
Open8_Bus.Wr_Data <= Regfile(conv_integer(DP_Ctrl.Reg));
|
1135 |
169 |
jshamlet |
|
1136 |
|
|
when DATA_WR_FLAG =>
|
1137 |
223 |
jshamlet |
Open8_Bus.Wr_En <= '1';
|
1138 |
|
|
Open8_Bus.Wr_Data <= Flags;
|
1139 |
169 |
jshamlet |
|
1140 |
|
|
when DATA_WR_PC =>
|
1141 |
223 |
jshamlet |
Open8_Bus.Wr_En <= '1';
|
1142 |
|
|
Open8_Bus.Wr_Data <= Program_Ctr(15 downto 8);
|
1143 |
182 |
jshamlet |
if( DP_Ctrl.Reg = PC_LSB )then
|
1144 |
223 |
jshamlet |
Open8_Bus.Wr_Data <= Program_Ctr(7 downto 0);
|
1145 |
169 |
jshamlet |
end if;
|
1146 |
|
|
|
1147 |
|
|
when others =>
|
1148 |
|
|
null;
|
1149 |
|
|
end case;
|
1150 |
|
|
|
1151 |
|
|
-------------------------------------------------------------------------------
|
1152 |
|
|
-- Stack Pointer
|
1153 |
|
|
-------------------------------------------------------------------------------
|
1154 |
|
|
case SP_Ctrl.Oper is
|
1155 |
|
|
when SP_IDLE =>
|
1156 |
|
|
null;
|
1157 |
|
|
|
1158 |
181 |
jshamlet |
when SP_CLR =>
|
1159 |
169 |
jshamlet |
Stack_Ptr <= Stack_Start_Addr;
|
1160 |
|
|
|
1161 |
181 |
jshamlet |
when SP_SET =>
|
1162 |
245 |
jshamlet |
if( Supervisor_Mode )then
|
1163 |
|
|
if( Flags(PSR_I) = '1' )then
|
1164 |
|
|
Stack_Ptr <= Regfile(1) & Regfile(0);
|
1165 |
|
|
end if;
|
1166 |
|
|
else
|
1167 |
|
|
Stack_Ptr <= Regfile(1) & Regfile(0);
|
1168 |
|
|
end if;
|
1169 |
181 |
jshamlet |
|
1170 |
169 |
jshamlet |
when SP_POP =>
|
1171 |
|
|
Stack_Ptr <= Stack_Ptr + 1;
|
1172 |
|
|
|
1173 |
|
|
when SP_PUSH =>
|
1174 |
|
|
Stack_Ptr <= Stack_Ptr - 1;
|
1175 |
|
|
|
1176 |
|
|
when others =>
|
1177 |
|
|
null;
|
1178 |
|
|
|
1179 |
|
|
end case;
|
1180 |
|
|
|
1181 |
|
|
-------------------------------------------------------------------------------
|
1182 |
|
|
-- Interrupt Controller
|
1183 |
|
|
-------------------------------------------------------------------------------
|
1184 |
245 |
jshamlet |
|
1185 |
|
|
-- If Supervisor_Mode is set, restrict the SMSK instruction such that it
|
1186 |
|
|
-- requires the I bit to be set.
|
1187 |
|
|
if( Supervisor_Mode )then
|
1188 |
|
|
Set_Mask <= INT_Ctrl.Mask_Set and Flags(PSR_I);
|
1189 |
|
|
else
|
1190 |
|
|
Set_Mask <= INT_Ctrl.Mask_Set;
|
1191 |
|
|
end if;
|
1192 |
|
|
|
1193 |
169 |
jshamlet |
-- The interrupt control mask is always sourced out of R0
|
1194 |
245 |
jshamlet |
if( Set_Mask = '1' )then
|
1195 |
169 |
jshamlet |
if( Enable_NMI )then
|
1196 |
|
|
Int_Mask <= Regfile(conv_integer(ACCUM))(7 downto 1) & '1';
|
1197 |
|
|
else
|
1198 |
|
|
Int_Mask <= Regfile(conv_integer(ACCUM));
|
1199 |
|
|
end if;
|
1200 |
|
|
end if;
|
1201 |
|
|
|
1202 |
|
|
-- Combine external and internal interrupts, and mask the OR of the two
|
1203 |
|
|
-- with the mask. Record any incoming interrupts to the pending buffer
|
1204 |
|
|
i_Ints := (Interrupts or INT_Ctrl.Soft_Ints) and
|
1205 |
|
|
Int_Mask;
|
1206 |
172 |
jshamlet |
|
1207 |
169 |
jshamlet |
Pending <= i_Ints or Pending;
|
1208 |
|
|
|
1209 |
210 |
jshamlet |
if( Sequential_Interrupts )then
|
1210 |
|
|
Wait_for_ISR <= Flags(PSR_I);
|
1211 |
|
|
else
|
1212 |
|
|
Wait_for_ISR <= '0';
|
1213 |
|
|
end if;
|
1214 |
|
|
|
1215 |
|
|
if( Wait_for_FSM = '0' and Wait_for_ISR = '0' )then
|
1216 |
169 |
jshamlet |
if( Pending(0) = '1' )then
|
1217 |
|
|
ISR_Addr <= INT_VECTOR_0;
|
1218 |
|
|
Pending(0) <= '0';
|
1219 |
|
|
elsif( Pending(1) = '1' )then
|
1220 |
|
|
ISR_Addr <= INT_VECTOR_1;
|
1221 |
|
|
Pending(1) <= '0';
|
1222 |
|
|
elsif( Pending(2) = '1' )then
|
1223 |
|
|
ISR_Addr <= INT_VECTOR_2;
|
1224 |
|
|
Pending(2) <= '0';
|
1225 |
|
|
elsif( Pending(3) = '1' )then
|
1226 |
|
|
ISR_Addr <= INT_VECTOR_3;
|
1227 |
|
|
Pending(3) <= '0';
|
1228 |
|
|
elsif( Pending(4) = '1' )then
|
1229 |
|
|
ISR_Addr <= INT_VECTOR_4;
|
1230 |
|
|
Pending(4) <= '0';
|
1231 |
|
|
elsif( Pending(5) = '1' )then
|
1232 |
|
|
ISR_Addr <= INT_VECTOR_5;
|
1233 |
|
|
Pending(5) <= '0';
|
1234 |
|
|
elsif( Pending(6) = '1' )then
|
1235 |
|
|
ISR_Addr <= INT_VECTOR_6;
|
1236 |
|
|
Pending(6) <= '0';
|
1237 |
|
|
elsif( Pending(7) = '1' )then
|
1238 |
|
|
ISR_Addr <= INT_VECTOR_7;
|
1239 |
|
|
Pending(7) <= '0';
|
1240 |
|
|
end if;
|
1241 |
185 |
jshamlet |
Wait_for_FSM <= or_reduce(Pending);
|
1242 |
169 |
jshamlet |
end if;
|
1243 |
|
|
|
1244 |
|
|
-- Reset the Wait_for_FSM flag on Int_Ack
|
1245 |
|
|
Ack_Q <= Ack_D;
|
1246 |
|
|
Ack_Q1 <= Ack_Q;
|
1247 |
|
|
Int_Ack <= Ack_Q1;
|
1248 |
|
|
if( Int_Ack = '1' )then
|
1249 |
|
|
Wait_for_FSM <= '0';
|
1250 |
|
|
end if;
|
1251 |
|
|
|
1252 |
|
|
Int_Req <= Wait_for_FSM and (not Int_Ack);
|
1253 |
|
|
|
1254 |
|
|
-- Incr_ISR allows the CPU Core to advance the vector address to pop the
|
1255 |
|
|
-- lower half of the address.
|
1256 |
|
|
if( INT_Ctrl.Incr_ISR = '1' )then
|
1257 |
|
|
ISR_Addr <= ISR_Addr + 1;
|
1258 |
|
|
end if;
|
1259 |
|
|
|
1260 |
|
|
-------------------------------------------------------------------------------
|
1261 |
|
|
-- ALU (Arithmetic / Logic Unit)
|
1262 |
|
|
-------------------------------------------------------------------------------
|
1263 |
|
|
Index := conv_integer(ALU_Ctrl.Reg);
|
1264 |
|
|
Sum := (others => '0');
|
1265 |
|
|
Temp := (others => '0');
|
1266 |
|
|
|
1267 |
|
|
case ALU_Ctrl.Oper is
|
1268 |
|
|
when ALU_INC => -- Rn = Rn + 1 : Flags N,C,Z
|
1269 |
|
|
Sum := ("0" & x"01") +
|
1270 |
|
|
("0" & Regfile(Index));
|
1271 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1272 |
|
|
Flags(PSR_C) <= Sum(8);
|
1273 |
209 |
jshamlet |
Flags(PSR_N) <= Sum(7);
|
1274 |
169 |
jshamlet |
Regfile(Index) <= Sum(7 downto 0);
|
1275 |
|
|
|
1276 |
|
|
when ALU_UPP => -- Rn = Rn + 1
|
1277 |
|
|
Sum := ("0" & x"01") +
|
1278 |
|
|
("0" & Regfile(Index));
|
1279 |
185 |
jshamlet |
Flags(PSR_C) <= Sum(8);
|
1280 |
169 |
jshamlet |
Regfile(Index) <= Sum(7 downto 0);
|
1281 |
|
|
|
1282 |
|
|
when ALU_UPP2 => -- Rn = Rn + C
|
1283 |
|
|
Sum := ("0" & x"00") +
|
1284 |
|
|
("0" & Regfile(Index)) +
|
1285 |
185 |
jshamlet |
Flags(PSR_C);
|
1286 |
|
|
Flags(PSR_C) <= Sum(8);
|
1287 |
169 |
jshamlet |
Regfile(Index) <= Sum(7 downto 0);
|
1288 |
|
|
|
1289 |
|
|
when ALU_ADC => -- R0 = R0 + Rn + C : Flags N,C,Z
|
1290 |
|
|
Sum := ("0" & Regfile(0)) +
|
1291 |
|
|
("0" & Regfile(Index)) +
|
1292 |
185 |
jshamlet |
Flags(PSR_C);
|
1293 |
|
|
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1294 |
|
|
Flags(PSR_C) <= Sum(8);
|
1295 |
|
|
Flags(PSR_N) <= Sum(7);
|
1296 |
169 |
jshamlet |
Regfile(0) <= Sum(7 downto 0);
|
1297 |
|
|
|
1298 |
|
|
when ALU_TX0 => -- R0 = Rn : Flags N,Z
|
1299 |
|
|
Temp := "0" & Regfile(Index);
|
1300 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1301 |
|
|
Flags(PSR_N) <= Temp(7);
|
1302 |
169 |
jshamlet |
Regfile(0) <= Temp(7 downto 0);
|
1303 |
|
|
|
1304 |
|
|
when ALU_OR => -- R0 = R0 | Rn : Flags N,Z
|
1305 |
|
|
Temp(7 downto 0) := Regfile(0) or Regfile(Index);
|
1306 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1307 |
|
|
Flags(PSR_N) <= Temp(7);
|
1308 |
169 |
jshamlet |
Regfile(0) <= Temp(7 downto 0);
|
1309 |
|
|
|
1310 |
|
|
when ALU_AND => -- R0 = R0 & Rn : Flags N,Z
|
1311 |
|
|
Temp(7 downto 0) := Regfile(0) and Regfile(Index);
|
1312 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1313 |
|
|
Flags(PSR_N) <= Temp(7);
|
1314 |
169 |
jshamlet |
Regfile(0) <= Temp(7 downto 0);
|
1315 |
|
|
|
1316 |
|
|
when ALU_XOR => -- R0 = R0 ^ Rn : Flags N,Z
|
1317 |
|
|
Temp(7 downto 0) := Regfile(0) xor Regfile(Index);
|
1318 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1319 |
|
|
Flags(PSR_N) <= Temp(7);
|
1320 |
169 |
jshamlet |
Regfile(0) <= Temp(7 downto 0);
|
1321 |
|
|
|
1322 |
|
|
when ALU_ROL => -- Rn = Rn<<1,C : Flags N,C,Z
|
1323 |
185 |
jshamlet |
Temp := Regfile(Index) & Flags(PSR_C);
|
1324 |
|
|
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1325 |
|
|
Flags(PSR_C) <= Temp(8);
|
1326 |
|
|
Flags(PSR_N) <= Temp(7);
|
1327 |
169 |
jshamlet |
Regfile(Index) <= Temp(7 downto 0);
|
1328 |
|
|
|
1329 |
|
|
when ALU_ROR => -- Rn = C,Rn>>1 : Flags N,C,Z
|
1330 |
185 |
jshamlet |
Temp := Regfile(Index)(0) & Flags(PSR_C) &
|
1331 |
169 |
jshamlet |
Regfile(Index)(7 downto 1);
|
1332 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1333 |
|
|
Flags(PSR_C) <= Temp(8);
|
1334 |
|
|
Flags(PSR_N) <= Temp(7);
|
1335 |
169 |
jshamlet |
Regfile(Index) <= Temp(7 downto 0);
|
1336 |
|
|
|
1337 |
|
|
when ALU_DEC => -- Rn = Rn - 1 : Flags N,C,Z
|
1338 |
|
|
Sum := ("0" & Regfile(Index)) +
|
1339 |
|
|
("0" & x"FF");
|
1340 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1341 |
|
|
Flags(PSR_C) <= Sum(8);
|
1342 |
|
|
Flags(PSR_N) <= Sum(7);
|
1343 |
169 |
jshamlet |
Regfile(Index) <= Sum(7 downto 0);
|
1344 |
|
|
|
1345 |
|
|
when ALU_SBC => -- Rn = R0 - Rn - C : Flags N,C,Z
|
1346 |
|
|
Sum := ("0" & Regfile(0)) +
|
1347 |
|
|
("1" & (not Regfile(Index))) +
|
1348 |
185 |
jshamlet |
Flags(PSR_C);
|
1349 |
|
|
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1350 |
|
|
Flags(PSR_C) <= Sum(8);
|
1351 |
|
|
Flags(PSR_N) <= Sum(7);
|
1352 |
169 |
jshamlet |
Regfile(0) <= Sum(7 downto 0);
|
1353 |
|
|
|
1354 |
|
|
when ALU_ADD => -- R0 = R0 + Rn : Flags N,C,Z
|
1355 |
|
|
Sum := ("0" & Regfile(0)) +
|
1356 |
|
|
("0" & Regfile(Index));
|
1357 |
185 |
jshamlet |
Flags(PSR_C) <= Sum(8);
|
1358 |
169 |
jshamlet |
Regfile(0) <= Sum(7 downto 0);
|
1359 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1360 |
|
|
Flags(PSR_N) <= Sum(7);
|
1361 |
169 |
jshamlet |
|
1362 |
|
|
when ALU_STP => -- Sets bit(n) in the Flags register
|
1363 |
|
|
Flags(Index) <= '1';
|
1364 |
|
|
|
1365 |
|
|
when ALU_BTT => -- Z = !R0(N), N = R0(7)
|
1366 |
185 |
jshamlet |
Flags(PSR_Z) <= not Regfile(0)(Index);
|
1367 |
|
|
Flags(PSR_N) <= Regfile(0)(7);
|
1368 |
169 |
jshamlet |
|
1369 |
|
|
when ALU_CLP => -- Clears bit(n) in the Flags register
|
1370 |
|
|
Flags(Index) <= '0';
|
1371 |
|
|
|
1372 |
|
|
when ALU_T0X => -- Rn = R0 : Flags N,Z
|
1373 |
|
|
Temp := "0" & Regfile(0);
|
1374 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Temp(7 downto 0));
|
1375 |
|
|
Flags(PSR_N) <= Temp(7);
|
1376 |
169 |
jshamlet |
Regfile(Index) <= Temp(7 downto 0);
|
1377 |
|
|
|
1378 |
|
|
when ALU_CMP => -- Sets Flags on R0 - Rn : Flags N,C,Z
|
1379 |
|
|
Sum := ("0" & Regfile(0)) +
|
1380 |
|
|
("1" & (not Regfile(Index))) +
|
1381 |
|
|
'1';
|
1382 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Sum(7 downto 0));
|
1383 |
|
|
Flags(PSR_C) <= Sum(8);
|
1384 |
|
|
Flags(PSR_N) <= Sum(7);
|
1385 |
169 |
jshamlet |
|
1386 |
|
|
when ALU_MUL => -- Stage 1 of 2 {R1:R0} = R0 * Rn : Flags Z
|
1387 |
|
|
Regfile(0) <= Mult(7 downto 0);
|
1388 |
|
|
Regfile(1) <= Mult(15 downto 8);
|
1389 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Mult);
|
1390 |
169 |
jshamlet |
|
1391 |
|
|
when ALU_LDI => -- Rn <= Data : Flags N,Z
|
1392 |
185 |
jshamlet |
Flags(PSR_Z) <= nor_reduce(Operand1);
|
1393 |
|
|
Flags(PSR_N) <= Operand1(7);
|
1394 |
|
|
Regfile(Index) <= Operand1;
|
1395 |
169 |
jshamlet |
|
1396 |
|
|
when ALU_POP => -- Rn <= Data
|
1397 |
185 |
jshamlet |
Regfile(Index) <= Operand1;
|
1398 |
169 |
jshamlet |
|
1399 |
|
|
when ALU_RFLG =>
|
1400 |
188 |
jshamlet |
Flags(3 downto 0) <= Operand1(3 downto 0);
|
1401 |
|
|
if( not RTI_Ignores_GP_Flags )then
|
1402 |
|
|
Flags(7 downto 4)<= Operand1(7 downto 4);
|
1403 |
|
|
end if;
|
1404 |
169 |
jshamlet |
|
1405 |
185 |
jshamlet |
when ALU_RSP =>
|
1406 |
181 |
jshamlet |
Regfile(0) <= Stack_Ptr(7 downto 0);
|
1407 |
|
|
Regfile(1) <= Stack_Ptr(15 downto 8);
|
1408 |
|
|
|
1409 |
185 |
jshamlet |
when ALU_GMSK =>
|
1410 |
|
|
Flags(PSR_Z) <= nor_reduce(Int_Mask);
|
1411 |
|
|
Regfile(0) <= Int_Mask;
|
1412 |
|
|
|
1413 |
169 |
jshamlet |
when others =>
|
1414 |
|
|
null;
|
1415 |
|
|
end case;
|
1416 |
|
|
|
1417 |
224 |
jshamlet |
Open8_Bus.GP_Flags <= Flags(7 downto 3);
|
1418 |
188 |
jshamlet |
|
1419 |
169 |
jshamlet |
end if;
|
1420 |
|
|
end process;
|
1421 |
|
|
|
1422 |
182 |
jshamlet |
-------------------------------------------------------------------------------
|
1423 |
|
|
-- Multiplier Logic
|
1424 |
|
|
--
|
1425 |
|
|
-- We need to infer a hardware multipler, so we create a special clocked
|
1426 |
|
|
-- process with no reset or clock enable
|
1427 |
|
|
-------------------------------------------------------------------------------
|
1428 |
|
|
|
1429 |
|
|
Multiplier_proc: process( Clock )
|
1430 |
|
|
begin
|
1431 |
|
|
if( rising_edge(Clock) )then
|
1432 |
|
|
Mult <= Regfile(0) *
|
1433 |
186 |
jshamlet |
Regfile(conv_integer(ALU_Ctrl.Reg));
|
1434 |
|
|
end if;
|
1435 |
|
|
end process;
|
1436 |
|
|
|
1437 |
|
|
end architecture;
|