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jshamlet |
-- Copyright (c)2006,2011,2012,2013,2015 Jeremy Seth Henry
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-- 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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-- (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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-- SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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--
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-- VHDL Units : Open8_CPU
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-- 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 contents
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-- : of R1:R0 are used to initialize the stack pointer.
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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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-- : 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 WAIT_FOR_INT 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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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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use work.Open8_pkg.all;
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entity Open8_CPU is
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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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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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Default_Interrupt_Mask : DATA_TYPE := x"FF"; -- Enable all Ints
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Reset_Level : std_logic := '0' ); -- Active reset level
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port(
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Clock : in std_logic;
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Reset : in std_logic;
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Interrupts : in INTERRUPT_BUNDLE;
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--
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Address : out ADDRESS_TYPE;
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Rd_Data : in DATA_TYPE;
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Rd_Enable : out std_logic;
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Wr_Data : out DATA_TYPE;
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Wr_Enable : out std_logic );
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end entity;
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architecture behave of Open8_CPU is
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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;
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constant INT_VECTOR_6 : ADDRESS_TYPE := ISR_Start_Addr+12;
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constant INT_VECTOR_7 : ADDRESS_TYPE := ISR_Start_Addr+14;
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signal Halt : std_logic;
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signal CPU_Next_State : CPU_STATES := PIPE_FILL_0;
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signal CPU_State : CPU_STATES := PIPE_FILL_0;
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signal Cache_Ctrl : CACHE_MODES := CACHE_IDLE;
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signal Opcode : OPCODE_TYPE := (others => '0');
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signal SubOp, SubOp_p1 : SUBOP_TYPE := (others => '0');
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signal Prefetch : DATA_TYPE := x"00";
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signal Operand1, Operand2 : DATA_TYPE := x"00";
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signal Instr_Prefetch : std_logic := '0';
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signal PC_Ctrl : PC_CTRL_TYPE;
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signal Program_Ctr : ADDRESS_TYPE := x"0000";
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signal SP_Ctrl : SP_CTRL_TYPE;
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signal Stack_Ptr : ADDRESS_TYPE := x"0000";
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signal DP_Ctrl : DATA_CTRL_TYPE;
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signal INT_Ctrl : INT_CTRL_TYPE;
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signal Ack_D, Ack_Q, Ack_Q1: std_logic := '0';
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signal Int_Req, Int_Ack : std_logic := '0';
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signal Int_Mask : DATA_TYPE := x"00";
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signal ISR_Addr : ADDRESS_TYPE := x"0000";
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signal i_Ints : INTERRUPT_BUNDLE := x"00";
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signal Pending : INTERRUPT_BUNDLE := x"00";
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signal Wait_for_FSM : std_logic := '0';
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signal ALU_Ctrl : ALU_CTRL_TYPE;
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signal Regfile : REGFILE_TYPE;
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signal Flags : FLAG_TYPE;
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signal Mult : ADDRESS_TYPE := x"0000";
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begin
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-------------------------------------------------------------------------------
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-- State Logic / Instruction Decoding & Execution
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-- Combinatorial portion of CPU finite state machine
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-------------------------------------------------------------------------------
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State_Logic: process(CPU_State, Regfile, Flags, Int_Mask, Opcode,
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SubOp , SubOp_p1, Operand1, Operand2, Int_Req,
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Program_Ctr, Stack_Ptr, ISR_Addr )
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variable Reg, Reg_1 : integer range 0 to 7 := 0;
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variable Offset_SX : ADDRESS_TYPE;
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begin
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CPU_Next_State <= CPU_State;
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Cache_Ctrl <= CACHE_IDLE;
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--
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ALU_Ctrl.Oper <= ALU_IDLE;
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ALU_Ctrl.Reg <= ACCUM;
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ALU_Ctrl.Data <= x"00";
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--
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PC_Ctrl.Oper <= PC_IDLE;
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PC_Ctrl.Offset <= x"03";
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PC_Ctrl.Addr <= x"0000";
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--
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SP_Ctrl.Oper <= SP_IDLE;
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--
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Address <= Program_Ctr;
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--
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DP_Ctrl.Src <= DATA_RD_MEM;
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DP_Ctrl.Reg <= ACCUM;
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--
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INT_Ctrl.Mask_Set <= '0';
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INT_Ctrl.Soft_Ints <= x"00";
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INT_Ctrl.Incr_ISR <= '0';
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Ack_D <= '0';
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-- Assign the most common value of Reg and Reg1 outside the case structure
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-- to simplify things.
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Reg := conv_integer(SubOp);
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Reg_1 := conv_integer(SubOp_p1);
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Offset_SX(15 downto 0) := (others => Operand1(7));
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Offset_SX(7 downto 0) := Operand1;
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case CPU_State is
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-------------------------------------------------------------------------------
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-- Initial Instruction fetch & decode
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-------------------------------------------------------------------------------
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when PIPE_FILL_0 =>
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CPU_Next_State <= PIPE_FILL_1;
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PC_Ctrl.Oper <= PC_INCR;
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when PIPE_FILL_1 =>
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CPU_Next_State <= PIPE_FILL_2;
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PC_Ctrl.Oper <= PC_INCR;
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when PIPE_FILL_2 =>
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CPU_Next_State <= INSTR_DECODE;
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Cache_Ctrl <= CACHE_INSTR;
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PC_Ctrl.Oper <= PC_INCR;
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when INSTR_DECODE =>
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CPU_Next_State <= INSTR_DECODE;
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Cache_Ctrl <= CACHE_INSTR;
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case Opcode is
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when OP_PSH =>
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CPU_Next_State <= PSH_C1;
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Cache_Ctrl <= CACHE_PREFETCH;
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PC_Ctrl.Oper <= PC_REV1;
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DP_Ctrl.Src <= DATA_WR_REG;
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DP_Ctrl.Reg <= SubOp;
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when OP_POP =>
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CPU_Next_State <= POP_C1;
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Cache_Ctrl <= CACHE_PREFETCH;
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PC_Ctrl.Oper <= PC_REV2;
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SP_Ctrl.Oper <= SP_POP;
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when OP_BR0 | OP_BR1 =>
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CPU_Next_State <= BRN_C1;
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Cache_Ctrl <= CACHE_OPER1;
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PC_Ctrl.Oper <= PC_INCR;
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when OP_DBNZ =>
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CPU_Next_State <= DBNZ_C1;
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Cache_Ctrl <= CACHE_OPER1;
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PC_Ctrl.Oper <= PC_INCR;
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ALU_Ctrl.Oper <= ALU_DEC;
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ALU_Ctrl.Reg <= SubOp;
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when OP_INT =>
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PC_Ctrl.Oper <= PC_INCR;
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-- Make sure the requested interrupt is actually enabled first
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if( Int_Mask(Reg) = '1' )then
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|
|
CPU_Next_State <= WAIT_FOR_INT;
|
324 |
|
|
INT_Ctrl.Soft_Ints(Reg) <= '1';
|
325 |
|
|
end if;
|
326 |
|
|
|
327 |
|
|
when OP_STK =>
|
328 |
|
|
case SubOp is
|
329 |
|
|
when SOP_RSP =>
|
330 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
331 |
|
|
SP_Ctrl.Oper <= SP_RSET;
|
332 |
|
|
|
333 |
|
|
when SOP_RTS | SOP_RTI =>
|
334 |
|
|
CPU_Next_State <= RTS_C1;
|
335 |
|
|
Cache_Ctrl <= CACHE_IDLE;
|
336 |
|
|
SP_Ctrl.Oper <= SP_POP;
|
337 |
|
|
|
338 |
|
|
when SOP_BRK =>
|
339 |
|
|
CPU_Next_State <= BRK_C1;
|
340 |
|
|
PC_Ctrl.Oper <= PC_REV2;
|
341 |
|
|
-- If Break implements Wait for Interrupt, replace the normal
|
342 |
|
|
-- flow with a modified version of the INT instruction
|
343 |
|
|
if( BRK_Implements_WAI )then
|
344 |
|
|
CPU_Next_State <= WAIT_FOR_INT;
|
345 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
346 |
|
|
end if;
|
347 |
|
|
|
348 |
|
|
when SOP_JMP =>
|
349 |
|
|
CPU_Next_State <= JMP_C1;
|
350 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
351 |
|
|
|
352 |
|
|
when SOP_SMSK =>
|
353 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
354 |
|
|
INT_Ctrl.Mask_Set <= '1';
|
355 |
|
|
|
356 |
|
|
when SOP_GMSK =>
|
357 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
358 |
|
|
ALU_Ctrl.Oper<= ALU_LDI;
|
359 |
|
|
ALU_Ctrl.Reg <= ACCUM;
|
360 |
|
|
ALU_Ctrl.Data<= Int_Mask;
|
361 |
|
|
|
362 |
|
|
when SOP_JSR =>
|
363 |
|
|
CPU_Next_State <= JSR_C1;
|
364 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
365 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
366 |
|
|
DP_Ctrl.Reg <= ACCUM+1;
|
367 |
|
|
|
368 |
|
|
when others => null;
|
369 |
|
|
end case;
|
370 |
|
|
|
371 |
|
|
when OP_MUL =>
|
372 |
|
|
CPU_Next_State <= MUL_C1;
|
373 |
|
|
-- We need to back the PC up by 1, and allow it to refill. An
|
374 |
|
|
-- unfortunate consequence of the pipelining. We can get away with
|
375 |
|
|
-- only 1 extra clock by pre-fetching the next instruction, though
|
376 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
377 |
|
|
PC_Ctrl.Oper <= PC_REV1;
|
378 |
|
|
-- Multiplication is automatic, but requires a single clock cycle.
|
379 |
|
|
-- We need to specify the register for Rn (R1:R0 = R0 * Rn) now,
|
380 |
|
|
-- but will issue the multiply command on the next clock to copy
|
381 |
|
|
-- the results to the specified register.
|
382 |
|
|
ALU_Ctrl.Oper <= ALU_IDLE;
|
383 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
384 |
|
|
|
385 |
|
|
when OP_UPP =>
|
386 |
|
|
CPU_Next_State <= UPP_C1;
|
387 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
388 |
|
|
PC_Ctrl.Oper <= PC_REV1;
|
389 |
|
|
ALU_Ctrl.Oper <= Opcode;
|
390 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
391 |
|
|
|
392 |
|
|
when OP_LDA =>
|
393 |
|
|
CPU_Next_State <= LDA_C1;
|
394 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
395 |
|
|
|
396 |
|
|
when OP_LDI =>
|
397 |
|
|
CPU_Next_State <= LDI_C1;
|
398 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
399 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
400 |
|
|
|
401 |
|
|
when OP_LDO =>
|
402 |
|
|
CPU_Next_State <= LDO_C1;
|
403 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
404 |
|
|
PC_Ctrl.Oper <= PC_REV2;
|
405 |
|
|
|
406 |
|
|
when OP_LDX =>
|
407 |
|
|
CPU_Next_State <= LDX_C1;
|
408 |
|
|
PC_Ctrl.Oper <= PC_REV2;
|
409 |
|
|
-- If auto-increment is disabled, use the specified register pair,
|
410 |
|
|
-- otherwise, for an odd:even pair, and issue the first half of
|
411 |
|
|
-- a UPP instruction to the ALU
|
412 |
|
|
if( not Enable_Auto_Increment )then
|
413 |
|
|
Address <= Regfile(Reg_1) & Regfile(Reg);
|
414 |
|
|
else
|
415 |
|
|
Reg := conv_integer(SubOp(2 downto 1) & '0');
|
416 |
|
|
Reg_1 := conv_integer(SubOp(2 downto 1) & '1');
|
417 |
|
|
Address <= Regfile(Reg_1) & Regfile(Reg);
|
418 |
|
|
if( SubOp(0) = '1' )then
|
419 |
|
|
ALU_Ctrl.Oper<= ALU_UPP;
|
420 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
421 |
|
|
end if;
|
422 |
|
|
end if;
|
423 |
|
|
|
424 |
|
|
when OP_STA =>
|
425 |
|
|
CPU_Next_State <= STA_C1;
|
426 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
427 |
|
|
|
428 |
|
|
when OP_STO =>
|
429 |
|
|
CPU_Next_State <= STO_C1;
|
430 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
431 |
|
|
PC_Ctrl.Oper <= PC_REV2;
|
432 |
|
|
DP_Ctrl.Src <= DATA_WR_REG;
|
433 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
434 |
|
|
|
435 |
|
|
when OP_STX =>
|
436 |
|
|
CPU_Next_State <= STX_C1;
|
437 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
438 |
|
|
PC_Ctrl.Oper <= PC_REV2;
|
439 |
|
|
DP_Ctrl.Src <= DATA_WR_REG;
|
440 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
441 |
|
|
|
442 |
|
|
when others =>
|
443 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
444 |
|
|
ALU_Ctrl.Oper <= Opcode;
|
445 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
446 |
|
|
|
447 |
|
|
end case;
|
448 |
|
|
|
449 |
|
|
-------------------------------------------------------------------------------
|
450 |
|
|
-- Program Control (BR0_C1, BR1_C1, DBNZ_C1, JMP )
|
451 |
|
|
-------------------------------------------------------------------------------
|
452 |
|
|
|
453 |
|
|
when BRN_C1 =>
|
454 |
|
|
CPU_Next_State <= INSTR_DECODE;
|
455 |
|
|
Cache_Ctrl <= CACHE_INSTR;
|
456 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
457 |
|
|
if( Flags(Reg) = Opcode(0) )then
|
458 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
459 |
|
|
Cache_Ctrl <= CACHE_IDLE;
|
460 |
|
|
PC_Ctrl.Offset <= Operand1;
|
461 |
|
|
end if;
|
462 |
|
|
|
463 |
|
|
when DBNZ_C1 =>
|
464 |
|
|
CPU_Next_State <= INSTR_DECODE;
|
465 |
|
|
Cache_Ctrl <= CACHE_INSTR;
|
466 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
467 |
|
|
if( Flags(FL_ZERO) = '0' )then
|
468 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
469 |
|
|
Cache_Ctrl <= CACHE_IDLE;
|
470 |
|
|
PC_Ctrl.Offset <= Operand1;
|
471 |
|
|
end if;
|
472 |
|
|
|
473 |
|
|
when JMP_C1 =>
|
474 |
|
|
CPU_Next_State <= JMP_C2;
|
475 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
476 |
|
|
|
477 |
|
|
when JMP_C2 =>
|
478 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
479 |
|
|
PC_Ctrl.Oper <= PC_LOAD;
|
480 |
|
|
PC_Ctrl.Addr <= Operand2 & Operand1;
|
481 |
|
|
|
482 |
|
|
-------------------------------------------------------------------------------
|
483 |
|
|
-- Data Storage - Load from memory (LDA, LDI, LDO, LDX)
|
484 |
|
|
-------------------------------------------------------------------------------
|
485 |
|
|
|
486 |
|
|
when LDA_C1 =>
|
487 |
|
|
CPU_Next_State <= LDA_C2;
|
488 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
489 |
|
|
|
490 |
|
|
when LDA_C2 =>
|
491 |
|
|
CPU_Next_State <= LDA_C3;
|
492 |
|
|
Address <= Operand2 & Operand1;
|
493 |
|
|
|
494 |
|
|
when LDA_C3 =>
|
495 |
|
|
CPU_Next_State <= LDA_C4;
|
496 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
497 |
|
|
|
498 |
|
|
when LDA_C4 =>
|
499 |
|
|
CPU_Next_State <= LDI_C1;
|
500 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
501 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
502 |
|
|
|
503 |
|
|
when LDI_C1 =>
|
504 |
|
|
CPU_Next_State <= INSTR_DECODE;
|
505 |
|
|
Cache_Ctrl <= CACHE_INSTR;
|
506 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
507 |
|
|
ALU_Ctrl.Oper <= ALU_LDI;
|
508 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
509 |
|
|
ALU_Ctrl.Data <= Operand1;
|
510 |
|
|
|
511 |
|
|
when LDO_C1 =>
|
512 |
|
|
CPU_Next_State <= LDX_C1;
|
513 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
514 |
|
|
if( Enable_Auto_Increment )then
|
515 |
|
|
Reg := conv_integer(SubOp(2 downto 1) & '0');
|
516 |
|
|
Reg_1 := conv_integer(SubOp(2 downto 1) & '1');
|
517 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg)) + Offset_SX;
|
518 |
|
|
if( SubOp(0) = '1' )then
|
519 |
|
|
ALU_Ctrl.Oper<= ALU_UPP;
|
520 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
521 |
|
|
end if;
|
522 |
|
|
else
|
523 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg)) + Offset_SX;
|
524 |
|
|
end if;
|
525 |
|
|
|
526 |
|
|
when LDX_C1 =>
|
527 |
|
|
CPU_Next_State <= LDX_C2;
|
528 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
529 |
|
|
|
530 |
|
|
when LDX_C2 =>
|
531 |
|
|
CPU_Next_State <= LDX_C3;
|
532 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
533 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
534 |
|
|
|
535 |
|
|
when LDX_C3 =>
|
536 |
|
|
CPU_Next_State <= INSTR_DECODE;
|
537 |
|
|
Cache_Ctrl <= CACHE_INSTR;
|
538 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
539 |
|
|
ALU_Ctrl.Oper <= ALU_LDX;
|
540 |
|
|
ALU_Ctrl.Reg <= ACCUM;
|
541 |
|
|
ALU_Ctrl.Data <= Operand1;
|
542 |
|
|
|
543 |
|
|
-------------------------------------------------------------------------------
|
544 |
|
|
-- Data Storage - Store to memory (STA, STO, STX)
|
545 |
|
|
-------------------------------------------------------------------------------
|
546 |
|
|
when STA_C1 =>
|
547 |
|
|
CPU_Next_State <= STA_C2;
|
548 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
549 |
|
|
DP_Ctrl.Src <= DATA_WR_REG;
|
550 |
|
|
DP_Ctrl.Reg <= SubOp;
|
551 |
|
|
|
552 |
|
|
when STA_C2 =>
|
553 |
|
|
CPU_Next_State <= STA_C3;
|
554 |
|
|
Address <= Operand2 & Operand1;
|
555 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
556 |
|
|
|
557 |
|
|
when STA_C3 =>
|
558 |
|
|
CPU_Next_State <= PIPE_FILL_2;
|
559 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
560 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
561 |
|
|
|
562 |
|
|
when STO_C1 =>
|
563 |
|
|
Cache_Ctrl <= CACHE_PREFETCH;
|
564 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
565 |
|
|
-- If auto-increment is disabled, just load the registers normally
|
566 |
|
|
if( not Enable_Auto_Increment )then
|
567 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
568 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg)) + Offset_SX;
|
569 |
|
|
-- Otherwise, enforce the even register rule, and check the LSB to see
|
570 |
|
|
-- if we should perform the auto-increment on the register pair
|
571 |
|
|
else
|
572 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
573 |
|
|
Reg := conv_integer(SubOp(2 downto 1) & '0');
|
574 |
|
|
Reg_1 := conv_integer(SubOp(2 downto 1) & '1');
|
575 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg)) + Offset_SX;
|
576 |
|
|
if( SubOp(0) = '1' )then
|
577 |
|
|
CPU_Next_State <= STO_C2;
|
578 |
|
|
ALU_Ctrl.Oper <= ALU_UPP;
|
579 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
580 |
|
|
end if;
|
581 |
|
|
end if;
|
582 |
|
|
|
583 |
|
|
when STO_C2 =>
|
584 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
585 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
586 |
|
|
ALU_Ctrl.Oper <= ALU_UPP2;
|
587 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '1';
|
588 |
|
|
|
589 |
|
|
when STX_C1 =>
|
590 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
591 |
|
|
-- If auto-increment is disabled, just load the registers normally
|
592 |
|
|
if( not Enable_Auto_Increment )then
|
593 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
594 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg));
|
595 |
|
|
-- Otherwise, enforce the even register rule, and check the LSB to see
|
596 |
|
|
-- if we should perform the auto-increment on the register pair
|
597 |
|
|
else
|
598 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
599 |
|
|
Reg := conv_integer(SubOp(2 downto 1) & '0');
|
600 |
|
|
Reg_1 := conv_integer(SubOp(2 downto 1) & '1');
|
601 |
|
|
Address <= (Regfile(Reg_1) & Regfile(Reg));
|
602 |
|
|
if( SubOp(0) = '1' )then
|
603 |
|
|
CPU_Next_State <= STX_C2;
|
604 |
|
|
ALU_Ctrl.Oper <= ALU_UPP;
|
605 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '0';
|
606 |
|
|
end if;
|
607 |
|
|
end if;
|
608 |
|
|
|
609 |
|
|
when STX_C2 =>
|
610 |
|
|
CPU_Next_State <= PIPE_FILL_2;
|
611 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
612 |
|
|
ALU_Ctrl.Oper <= ALU_UPP2;
|
613 |
|
|
ALU_Ctrl.Reg <= SubOp(2 downto 1) & '1';
|
614 |
|
|
|
615 |
|
|
-------------------------------------------------------------------------------
|
616 |
|
|
-- Multi-Cycle Math Operations (UPP, MUL)
|
617 |
|
|
-------------------------------------------------------------------------------
|
618 |
|
|
|
619 |
|
|
-- Because we have to backup the pipeline by 1 to refetch the 2nd
|
620 |
|
|
-- instruction/first operand, we have to return through PF2
|
621 |
|
|
when MUL_C1 =>
|
622 |
|
|
CPU_Next_State <= PIPE_FILL_2;
|
623 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
624 |
|
|
ALU_Ctrl.Oper <= ALU_MUL;
|
625 |
|
|
|
626 |
|
|
when UPP_C1 =>
|
627 |
|
|
CPU_Next_State <= PIPE_FILL_2;
|
628 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
629 |
|
|
ALU_Ctrl.Oper <= ALU_UPP2;
|
630 |
|
|
ALU_Ctrl.Reg <= SubOp_p1;
|
631 |
|
|
|
632 |
|
|
-------------------------------------------------------------------------------
|
633 |
|
|
-- Basic Stack Manipulation (PSH, POP, RSP)
|
634 |
|
|
-------------------------------------------------------------------------------
|
635 |
|
|
when PSH_C1 =>
|
636 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
637 |
|
|
Address <= Stack_Ptr;
|
638 |
|
|
SP_Ctrl.Oper <= SP_PUSH;
|
639 |
|
|
|
640 |
|
|
when POP_C1 =>
|
641 |
|
|
CPU_Next_State <= POP_C2;
|
642 |
|
|
Address <= Stack_Ptr;
|
643 |
|
|
|
644 |
|
|
when POP_C2 =>
|
645 |
|
|
CPU_Next_State <= POP_C3;
|
646 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
647 |
|
|
|
648 |
|
|
when POP_C3 =>
|
649 |
|
|
CPU_Next_State <= POP_C4;
|
650 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
651 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
652 |
|
|
|
653 |
|
|
when POP_C4 =>
|
654 |
|
|
CPU_Next_State <= INSTR_DECODE;
|
655 |
|
|
Cache_Ctrl <= CACHE_INSTR;
|
656 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
657 |
|
|
ALU_Ctrl.Oper <= ALU_POP;
|
658 |
|
|
ALU_Ctrl.Reg <= SubOp;
|
659 |
|
|
ALU_Ctrl.Data <= Operand1;
|
660 |
|
|
|
661 |
|
|
-------------------------------------------------------------------------------
|
662 |
|
|
-- Subroutines & Interrupts (RTS, JSR)
|
663 |
|
|
-------------------------------------------------------------------------------
|
664 |
|
|
when WAIT_FOR_INT => -- For soft interrupts only, halt the Program_Ctr
|
665 |
|
|
DP_Ctrl.Src <= DATA_BUS_IDLE;
|
666 |
|
|
CPU_Next_State <= WAIT_FOR_INT;
|
667 |
|
|
|
668 |
|
|
when ISR_C1 =>
|
669 |
|
|
CPU_Next_State <= ISR_C2;
|
670 |
|
|
Address <= ISR_Addr;
|
671 |
|
|
INT_Ctrl.Incr_ISR <= '1';
|
672 |
|
|
|
673 |
|
|
when ISR_C2 =>
|
674 |
|
|
CPU_Next_State <= ISR_C3;
|
675 |
|
|
Address <= ISR_Addr;
|
676 |
|
|
DP_Ctrl.Src <= DATA_WR_FLAG;
|
677 |
|
|
|
678 |
|
|
when ISR_C3 =>
|
679 |
|
|
CPU_Next_State <= JSR_C1;
|
680 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
681 |
|
|
Address <= Stack_Ptr;
|
682 |
|
|
SP_Ctrl.Oper <= SP_PUSH;
|
683 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
684 |
|
|
DP_Ctrl.Reg <= ACCUM+1;
|
685 |
|
|
ALU_Ctrl.Oper <= ALU_STP;
|
686 |
|
|
ALU_Ctrl.Reg <= INT_FLAG;
|
687 |
|
|
Ack_D <= '1';
|
688 |
|
|
|
689 |
|
|
when JSR_C1 =>
|
690 |
|
|
CPU_Next_State <= JSR_C2;
|
691 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
692 |
|
|
Address <= Stack_Ptr;
|
693 |
|
|
SP_Ctrl.Oper <= SP_PUSH;
|
694 |
|
|
DP_Ctrl.Src <= DATA_WR_PC;
|
695 |
|
|
DP_Ctrl.Reg <= ACCUM;
|
696 |
|
|
|
697 |
|
|
when JSR_C2 =>
|
698 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
699 |
|
|
Address <= Stack_Ptr;
|
700 |
|
|
SP_Ctrl.Oper <= SP_PUSH;
|
701 |
|
|
PC_Ctrl.Oper <= PC_LOAD;
|
702 |
|
|
PC_Ctrl.Addr <= Operand2 & Operand1;
|
703 |
|
|
|
704 |
|
|
when RTS_C1 =>
|
705 |
|
|
CPU_Next_State <= RTS_C2;
|
706 |
|
|
Address <= Stack_Ptr;
|
707 |
|
|
SP_Ctrl.Oper <= SP_POP;
|
708 |
|
|
|
709 |
|
|
when RTS_C2 =>
|
710 |
|
|
CPU_Next_State <= RTS_C3;
|
711 |
|
|
Address <= Stack_Ptr;
|
712 |
|
|
-- if this is an RTI, then we need to POP the flags
|
713 |
|
|
if( SubOp = SOP_RTI )then
|
714 |
|
|
SP_Ctrl.Oper <= SP_POP;
|
715 |
|
|
end if;
|
716 |
|
|
|
717 |
|
|
when RTS_C3 =>
|
718 |
|
|
CPU_Next_State <= RTS_C4;
|
719 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
720 |
|
|
-- It doesn't really matter what is on the address bus for RTS, while
|
721 |
|
|
-- it does for RTI, so we make this the default
|
722 |
|
|
Address <= Stack_Ptr;
|
723 |
|
|
|
724 |
|
|
when RTS_C4 =>
|
725 |
|
|
CPU_Next_State <= RTS_C5;
|
726 |
|
|
Cache_Ctrl <= CACHE_OPER2;
|
727 |
|
|
|
728 |
|
|
when RTS_C5 =>
|
729 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
730 |
|
|
PC_Ctrl.Oper <= PC_LOAD;
|
731 |
|
|
PC_Ctrl.Addr <= Operand2 & Operand1;
|
732 |
|
|
if( SubOp = SOP_RTI )then
|
733 |
|
|
CPU_Next_State <= RTI_C6;
|
734 |
|
|
Cache_Ctrl <= CACHE_OPER1;
|
735 |
|
|
end if;
|
736 |
|
|
|
737 |
|
|
when RTI_C6 =>
|
738 |
|
|
CPU_Next_State <= PIPE_FILL_1;
|
739 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
740 |
|
|
ALU_Ctrl.Oper <= ALU_RFLG;
|
741 |
|
|
ALU_Ctrl.Data <= Operand1;
|
742 |
|
|
|
743 |
|
|
-------------------------------------------------------------------------------
|
744 |
|
|
-- Debugging (BRK) Performs a 5-clock NOP
|
745 |
|
|
-------------------------------------------------------------------------------
|
746 |
|
|
when BRK_C1 =>
|
747 |
|
|
CPU_Next_State <= PIPE_FILL_0;
|
748 |
|
|
|
749 |
|
|
when others =>
|
750 |
|
|
null;
|
751 |
|
|
end case;
|
752 |
|
|
|
753 |
|
|
-- Interrupt service routines can only begin during the decode and wait
|
754 |
|
|
-- states to avoid corruption due to incomplete instruction execution
|
755 |
|
|
if( Int_Req = '1' )then
|
756 |
|
|
if( CPU_State = INSTR_DECODE or CPU_State = WAIT_FOR_INT )then
|
757 |
|
|
-- Reset all of the sub-block controls to IDLE, to avoid unintended
|
758 |
|
|
-- operation due to the current instruction
|
759 |
|
|
ALU_Ctrl.Oper <= ALU_IDLE;
|
760 |
|
|
Cache_Ctrl <= CACHE_IDLE;
|
761 |
|
|
SP_Ctrl.Oper <= SP_IDLE;
|
762 |
|
|
DP_Ctrl.Src <= DATA_RD_MEM;
|
763 |
|
|
INT_Ctrl.Soft_Ints <= (others => '0');
|
764 |
|
|
-- Rewind the PC by 3 to compensate for the pipeline registers
|
765 |
|
|
PC_Ctrl.Oper <= PC_INCR;
|
766 |
|
|
PC_Ctrl.Offset <= x"FF";
|
767 |
|
|
CPU_Next_State <= ISR_C1;
|
768 |
|
|
|
769 |
|
|
end if;
|
770 |
|
|
end if;
|
771 |
|
|
|
772 |
|
|
end process;
|
773 |
|
|
|
774 |
|
|
-- We need to infer a hardware multipler, so we create a special clocked
|
775 |
|
|
-- process with no reset or clock enable
|
776 |
|
|
Multiplier_proc: process( Clock )
|
777 |
|
|
begin
|
778 |
|
|
if( rising_edge(Clock) )then
|
779 |
|
|
Mult <= Regfile(0) *
|
780 |
|
|
Regfile(conv_integer(ALU_Ctrl.Reg));
|
781 |
|
|
end if;
|
782 |
|
|
end process;
|
783 |
|
|
|
784 |
|
|
-------------------------------------------------------------------------------
|
785 |
|
|
-- Registered portion of CPU finite state machine
|
786 |
|
|
-------------------------------------------------------------------------------
|
787 |
|
|
CPU_Regs: process( Reset, Clock )
|
788 |
|
|
variable Offset_SX : ADDRESS_TYPE;
|
789 |
|
|
variable i_Ints : INTERRUPT_BUNDLE := (others => '0');
|
790 |
|
|
variable Index : integer range 0 to 7 := 0;
|
791 |
|
|
variable Sum : std_logic_vector(8 downto 0) := "000000000";
|
792 |
|
|
variable Temp : std_logic_vector(8 downto 0) := "000000000";
|
793 |
|
|
begin
|
794 |
|
|
if( Reset = Reset_Level )then
|
795 |
|
|
CPU_State <= PIPE_FILL_0;
|
796 |
|
|
Opcode <= OP_INC;
|
797 |
|
|
SubOp <= ACCUM;
|
798 |
|
|
SubOp_p1 <= ACCUM;
|
799 |
|
|
Operand1 <= x"00";
|
800 |
|
|
Operand2 <= x"00";
|
801 |
|
|
Instr_Prefetch <= '0';
|
802 |
|
|
Prefetch <= x"00";
|
803 |
|
|
|
804 |
|
|
Wr_Data <= (others => '0');
|
805 |
|
|
Wr_Enable <= '0';
|
806 |
|
|
Rd_Enable <= '1';
|
807 |
|
|
|
808 |
|
|
Program_Ctr <= Program_Start_Addr;
|
809 |
|
|
Stack_Ptr <= Stack_Start_Addr;
|
810 |
|
|
|
811 |
|
|
Ack_Q <= '0';
|
812 |
|
|
Ack_Q1 <= '0';
|
813 |
|
|
Int_Ack <= '0';
|
814 |
|
|
|
815 |
|
|
Int_Req <= '0';
|
816 |
|
|
Pending <= x"00";
|
817 |
|
|
Wait_for_FSM <= '0';
|
818 |
|
|
if( Enable_NMI )then
|
819 |
|
|
Int_Mask <= Default_Interrupt_Mask(7 downto 1) & '1';
|
820 |
|
|
else
|
821 |
|
|
Int_Mask <= Default_Interrupt_Mask;
|
822 |
|
|
end if;
|
823 |
|
|
ISR_Addr <= INT_VECTOR_0;
|
824 |
|
|
|
825 |
|
|
for i in 0 to 7 loop
|
826 |
|
|
Regfile(i) <= (others => '0');
|
827 |
|
|
end loop;
|
828 |
|
|
Flags <= x"00";
|
829 |
|
|
|
830 |
|
|
elsif( rising_edge(Clock) )then
|
831 |
|
|
Wr_Enable <= '0';
|
832 |
|
|
Wr_Data <= x"00";
|
833 |
|
|
Rd_Enable <= '0';
|
834 |
|
|
|
835 |
|
|
-------------------------------------------------------------------------------
|
836 |
|
|
-- Instruction/Operand caching for pipelined memory access
|
837 |
|
|
-------------------------------------------------------------------------------
|
838 |
|
|
CPU_State <= CPU_Next_State;
|
839 |
|
|
case Cache_Ctrl is
|
840 |
|
|
when CACHE_INSTR =>
|
841 |
|
|
Opcode <= Rd_Data(7 downto 3);
|
842 |
|
|
SubOp <= Rd_Data(2 downto 0);
|
843 |
|
|
SubOp_p1 <= Rd_Data(2 downto 0) + 1;
|
844 |
|
|
if( Instr_Prefetch = '1' )then
|
845 |
|
|
Opcode <= Prefetch(7 downto 3);
|
846 |
|
|
SubOp <= Prefetch(2 downto 0);
|
847 |
|
|
SubOp_p1 <= Prefetch(2 downto 0) + 1;
|
848 |
|
|
Instr_Prefetch <= '0';
|
849 |
|
|
end if;
|
850 |
|
|
|
851 |
|
|
when CACHE_OPER1 =>
|
852 |
|
|
Operand1 <= Rd_Data;
|
853 |
|
|
|
854 |
|
|
when CACHE_OPER2 =>
|
855 |
|
|
Operand2 <= Rd_Data;
|
856 |
|
|
|
857 |
|
|
when CACHE_PREFETCH =>
|
858 |
|
|
Prefetch <= Rd_Data;
|
859 |
|
|
Instr_Prefetch <= '1';
|
860 |
|
|
|
861 |
|
|
when CACHE_IDLE =>
|
862 |
|
|
null;
|
863 |
|
|
end case;
|
864 |
|
|
|
865 |
|
|
-------------------------------------------------------------------------------
|
866 |
|
|
-- Program Counter
|
867 |
|
|
-------------------------------------------------------------------------------
|
868 |
|
|
Offset_SX(15 downto 8) := (others => PC_Ctrl.Offset(7));
|
869 |
|
|
Offset_SX(7 downto 0) := PC_Ctrl.Offset;
|
870 |
|
|
|
871 |
|
|
case PC_Ctrl.Oper is
|
872 |
|
|
when PC_IDLE =>
|
873 |
|
|
null;
|
874 |
|
|
|
875 |
|
|
when PC_REV1 =>
|
876 |
|
|
Program_Ctr <= Program_Ctr - 1;
|
877 |
|
|
|
878 |
|
|
when PC_REV2 =>
|
879 |
|
|
Program_Ctr <= Program_Ctr - 2;
|
880 |
|
|
|
881 |
|
|
when PC_INCR =>
|
882 |
|
|
Program_Ctr <= Program_Ctr + Offset_SX - 2;
|
883 |
|
|
|
884 |
|
|
when PC_LOAD =>
|
885 |
|
|
Program_Ctr <= PC_Ctrl.Addr;
|
886 |
|
|
|
887 |
|
|
when others =>
|
888 |
|
|
null;
|
889 |
|
|
end case;
|
890 |
|
|
|
891 |
|
|
-------------------------------------------------------------------------------
|
892 |
|
|
-- (Write) Data Path
|
893 |
|
|
-------------------------------------------------------------------------------
|
894 |
|
|
case DP_Ctrl.Src is
|
895 |
|
|
when DATA_BUS_IDLE =>
|
896 |
|
|
null;
|
897 |
|
|
|
898 |
|
|
when DATA_RD_MEM =>
|
899 |
|
|
Rd_Enable <= '1';
|
900 |
|
|
|
901 |
|
|
when DATA_WR_REG =>
|
902 |
|
|
Wr_Enable <= '1';
|
903 |
|
|
Wr_Data <= Regfile(conv_integer(DP_Ctrl.Reg));
|
904 |
|
|
|
905 |
|
|
when DATA_WR_FLAG =>
|
906 |
|
|
Wr_Enable <= '1';
|
907 |
|
|
Wr_Data <= Flags;
|
908 |
|
|
|
909 |
|
|
when DATA_WR_PC =>
|
910 |
|
|
Wr_Enable <= '1';
|
911 |
|
|
Wr_Data <= Program_Ctr(15 downto 8);
|
912 |
|
|
if( DP_Ctrl.Reg = ACCUM )then
|
913 |
|
|
Wr_Data <= Program_Ctr(7 downto 0);
|
914 |
|
|
end if;
|
915 |
|
|
|
916 |
|
|
when others =>
|
917 |
|
|
null;
|
918 |
|
|
end case;
|
919 |
|
|
|
920 |
|
|
-------------------------------------------------------------------------------
|
921 |
|
|
-- Stack Pointer
|
922 |
|
|
-------------------------------------------------------------------------------
|
923 |
|
|
case SP_Ctrl.Oper is
|
924 |
|
|
when SP_IDLE =>
|
925 |
|
|
null;
|
926 |
|
|
|
927 |
|
|
when SP_RSET =>
|
928 |
|
|
-- The original RSP instruction simply reset the stack pointer to the preset
|
929 |
|
|
-- address set at compile time. However, with little extra effort, we can
|
930 |
|
|
-- modify the instruction to allow the stack pointer to be moved anywhere in
|
931 |
|
|
-- the memory map. Since RSP can't have an sub-opcode, R1:R0 was chosen as
|
932 |
|
|
-- a fixed source
|
933 |
|
|
Stack_Ptr <= Stack_Start_Addr;
|
934 |
|
|
if( Allow_Stack_Address_Move )then
|
935 |
|
|
Stack_Ptr <= Regfile(1) & Regfile(0);
|
936 |
|
|
end if;
|
937 |
|
|
|
938 |
|
|
when SP_POP =>
|
939 |
|
|
Stack_Ptr <= Stack_Ptr + 1;
|
940 |
|
|
|
941 |
|
|
when SP_PUSH =>
|
942 |
|
|
Stack_Ptr <= Stack_Ptr - 1;
|
943 |
|
|
|
944 |
|
|
when others =>
|
945 |
|
|
null;
|
946 |
|
|
|
947 |
|
|
end case;
|
948 |
|
|
|
949 |
|
|
-------------------------------------------------------------------------------
|
950 |
|
|
-- Interrupt Controller
|
951 |
|
|
-------------------------------------------------------------------------------
|
952 |
|
|
-- The interrupt control mask is always sourced out of R0
|
953 |
|
|
if( INT_Ctrl.Mask_Set = '1' )then
|
954 |
|
|
-- If the Enable_NMI generic is set, force the LSB high
|
955 |
|
|
if( Enable_NMI )then
|
956 |
|
|
Int_Mask <= Regfile(conv_integer(ACCUM))(7 downto 1) & '1';
|
957 |
|
|
else
|
958 |
|
|
Int_Mask <= Regfile(conv_integer(ACCUM));
|
959 |
|
|
end if;
|
960 |
|
|
end if;
|
961 |
|
|
|
962 |
|
|
-- Combine external and internal interrupts, and mask the OR of the two
|
963 |
|
|
-- with the mask. Record any incoming interrupts to the pending buffer
|
964 |
|
|
i_Ints := (Interrupts or INT_Ctrl.Soft_Ints) and
|
965 |
|
|
Int_Mask;
|
966 |
|
|
|
967 |
|
|
Pending <= i_Ints or Pending;
|
968 |
|
|
|
969 |
|
|
if( Wait_for_FSM = '0' )then
|
970 |
|
|
if( Pending(0) = '1' )then
|
971 |
|
|
ISR_Addr <= INT_VECTOR_0;
|
972 |
|
|
Pending(0) <= '0';
|
973 |
|
|
Wait_for_FSM <= '1';
|
974 |
|
|
elsif( Pending(1) = '1' )then
|
975 |
|
|
ISR_Addr <= INT_VECTOR_1;
|
976 |
|
|
Pending(1) <= '0';
|
977 |
|
|
Wait_for_FSM <= '1';
|
978 |
|
|
elsif( Pending(2) = '1' )then
|
979 |
|
|
ISR_Addr <= INT_VECTOR_2;
|
980 |
|
|
Pending(2) <= '0';
|
981 |
|
|
Wait_for_FSM <= '1';
|
982 |
|
|
elsif( Pending(3) = '1' )then
|
983 |
|
|
ISR_Addr <= INT_VECTOR_3;
|
984 |
|
|
Pending(3) <= '0';
|
985 |
|
|
Wait_for_FSM <= '1';
|
986 |
|
|
elsif( Pending(4) = '1' )then
|
987 |
|
|
ISR_Addr <= INT_VECTOR_4;
|
988 |
|
|
Pending(4) <= '0';
|
989 |
|
|
Wait_for_FSM <= '1';
|
990 |
|
|
elsif( Pending(5) = '1' )then
|
991 |
|
|
ISR_Addr <= INT_VECTOR_5;
|
992 |
|
|
Pending(5) <= '0';
|
993 |
|
|
Wait_for_FSM <= '1';
|
994 |
|
|
elsif( Pending(6) = '1' )then
|
995 |
|
|
ISR_Addr <= INT_VECTOR_6;
|
996 |
|
|
Pending(6) <= '0';
|
997 |
|
|
Wait_for_FSM <= '1';
|
998 |
|
|
elsif( Pending(7) = '1' )then
|
999 |
|
|
ISR_Addr <= INT_VECTOR_7;
|
1000 |
|
|
Pending(7) <= '0';
|
1001 |
|
|
Wait_for_FSM <= '1';
|
1002 |
|
|
end if;
|
1003 |
|
|
end if;
|
1004 |
|
|
|
1005 |
|
|
-- Reset the Wait_for_FSM flag on Int_Ack
|
1006 |
|
|
Ack_Q <= Ack_D;
|
1007 |
|
|
Ack_Q1 <= Ack_Q;
|
1008 |
|
|
Int_Ack <= Ack_Q1;
|
1009 |
|
|
if( Int_Ack = '1' )then
|
1010 |
|
|
Wait_for_FSM <= '0';
|
1011 |
|
|
end if;
|
1012 |
|
|
|
1013 |
|
|
Int_Req <= Wait_for_FSM and (not Int_Ack);
|
1014 |
|
|
|
1015 |
|
|
-- Incr_ISR allows the CPU Core to advance the vector address to pop the
|
1016 |
|
|
-- lower half of the address.
|
1017 |
|
|
if( INT_Ctrl.Incr_ISR = '1' )then
|
1018 |
|
|
ISR_Addr <= ISR_Addr + 1;
|
1019 |
|
|
end if;
|
1020 |
|
|
|
1021 |
|
|
-------------------------------------------------------------------------------
|
1022 |
|
|
-- ALU (Arithmetic / Logic Unit)
|
1023 |
|
|
-------------------------------------------------------------------------------
|
1024 |
|
|
Index := conv_integer(ALU_Ctrl.Reg);
|
1025 |
|
|
Sum := (others => '0');
|
1026 |
|
|
Temp := (others => '0');
|
1027 |
|
|
|
1028 |
|
|
case ALU_Ctrl.Oper is
|
1029 |
|
|
when ALU_INC => -- Rn = Rn + 1 : Flags N,C,Z
|
1030 |
|
|
Sum := ("0" & x"01") +
|
1031 |
|
|
("0" & Regfile(Index));
|
1032 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1033 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1034 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1035 |
|
|
Regfile(Index) <= Sum(7 downto 0);
|
1036 |
|
|
|
1037 |
|
|
when ALU_UPP => -- Rn = Rn + 1
|
1038 |
|
|
Sum := ("0" & x"01") +
|
1039 |
|
|
("0" & Regfile(Index));
|
1040 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1041 |
|
|
Regfile(Index) <= Sum(7 downto 0);
|
1042 |
|
|
|
1043 |
|
|
when ALU_UPP2 => -- Rn = Rn + C
|
1044 |
|
|
Sum := ("0" & x"00") +
|
1045 |
|
|
("0" & Regfile(Index)) +
|
1046 |
|
|
Flags(FL_CARRY);
|
1047 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1048 |
|
|
Regfile(Index) <= Sum(7 downto 0);
|
1049 |
|
|
|
1050 |
|
|
when ALU_ADC => -- R0 = R0 + Rn + C : Flags N,C,Z
|
1051 |
|
|
Sum := ("0" & Regfile(0)) +
|
1052 |
|
|
("0" & Regfile(Index)) +
|
1053 |
|
|
Flags(FL_CARRY);
|
1054 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1055 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1056 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1057 |
|
|
Regfile(0) <= Sum(7 downto 0);
|
1058 |
|
|
|
1059 |
|
|
when ALU_TX0 => -- R0 = Rn : Flags N,Z
|
1060 |
|
|
Temp := "0" & Regfile(Index);
|
1061 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1062 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1063 |
|
|
Regfile(0) <= Temp(7 downto 0);
|
1064 |
|
|
|
1065 |
|
|
when ALU_OR => -- R0 = R0 | Rn : Flags N,Z
|
1066 |
|
|
Temp(7 downto 0) := Regfile(0) or Regfile(Index);
|
1067 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1068 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1069 |
|
|
Regfile(0) <= Temp(7 downto 0);
|
1070 |
|
|
|
1071 |
|
|
when ALU_AND => -- R0 = R0 & Rn : Flags N,Z
|
1072 |
|
|
Temp(7 downto 0) := Regfile(0) and Regfile(Index);
|
1073 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1074 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1075 |
|
|
Regfile(0) <= Temp(7 downto 0);
|
1076 |
|
|
|
1077 |
|
|
when ALU_XOR => -- R0 = R0 ^ Rn : Flags N,Z
|
1078 |
|
|
Temp(7 downto 0) := Regfile(0) xor Regfile(Index);
|
1079 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1080 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1081 |
|
|
Regfile(0) <= Temp(7 downto 0);
|
1082 |
|
|
|
1083 |
|
|
when ALU_ROL => -- Rn = Rn<<1,C : Flags N,C,Z
|
1084 |
|
|
Temp := Regfile(Index) & Flags(FL_CARRY);
|
1085 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1086 |
|
|
Flags(FL_CARRY) <= Temp(8);
|
1087 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1088 |
|
|
Regfile(Index) <= Temp(7 downto 0);
|
1089 |
|
|
|
1090 |
|
|
when ALU_ROR => -- Rn = C,Rn>>1 : Flags N,C,Z
|
1091 |
|
|
Temp := Regfile(Index)(0) & Flags(FL_CARRY) &
|
1092 |
|
|
Regfile(Index)(7 downto 1);
|
1093 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1094 |
|
|
Flags(FL_CARRY) <= Temp(8);
|
1095 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1096 |
|
|
Regfile(Index) <= Temp(7 downto 0);
|
1097 |
|
|
|
1098 |
|
|
when ALU_DEC => -- Rn = Rn - 1 : Flags N,C,Z
|
1099 |
|
|
Sum := ("0" & Regfile(Index)) +
|
1100 |
|
|
("0" & x"FF");
|
1101 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1102 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1103 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1104 |
|
|
Regfile(Index) <= Sum(7 downto 0);
|
1105 |
|
|
|
1106 |
|
|
when ALU_SBC => -- Rn = R0 - Rn - C : Flags N,C,Z
|
1107 |
|
|
Sum := ("0" & Regfile(0)) +
|
1108 |
|
|
("1" & (not Regfile(Index))) +
|
1109 |
|
|
Flags(FL_CARRY);
|
1110 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1111 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1112 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1113 |
|
|
Regfile(0) <= Sum(7 downto 0);
|
1114 |
|
|
|
1115 |
|
|
when ALU_ADD => -- R0 = R0 + Rn : Flags N,C,Z
|
1116 |
|
|
Sum := ("0" & Regfile(0)) +
|
1117 |
|
|
("0" & Regfile(Index));
|
1118 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1119 |
|
|
Regfile(0) <= Sum(7 downto 0);
|
1120 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1121 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1122 |
|
|
|
1123 |
|
|
when ALU_STP => -- Sets bit(n) in the Flags register
|
1124 |
|
|
Flags(Index) <= '1';
|
1125 |
|
|
|
1126 |
|
|
when ALU_BTT => -- Z = !R0(N), N = R0(7)
|
1127 |
|
|
Flags(FL_ZERO) <= not Regfile(0)(Index);
|
1128 |
|
|
Flags(FL_NEG) <= Regfile(0)(7);
|
1129 |
|
|
|
1130 |
|
|
when ALU_CLP => -- Clears bit(n) in the Flags register
|
1131 |
|
|
Flags(Index) <= '0';
|
1132 |
|
|
|
1133 |
|
|
when ALU_T0X => -- Rn = R0 : Flags N,Z
|
1134 |
|
|
Temp := "0" & Regfile(0);
|
1135 |
|
|
Flags(FL_ZERO) <= nor_reduce(Temp(7 downto 0));
|
1136 |
|
|
Flags(FL_NEG) <= Temp(7);
|
1137 |
|
|
Regfile(Index) <= Temp(7 downto 0);
|
1138 |
|
|
|
1139 |
|
|
when ALU_CMP => -- Sets Flags on R0 - Rn : Flags N,C,Z
|
1140 |
|
|
Sum := ("0" & Regfile(0)) +
|
1141 |
|
|
("1" & (not Regfile(Index))) +
|
1142 |
|
|
'1';
|
1143 |
|
|
Flags(FL_ZERO) <= nor_reduce(Sum(7 downto 0));
|
1144 |
|
|
Flags(FL_CARRY) <= Sum(8);
|
1145 |
|
|
Flags(FL_NEG) <= Sum(7);
|
1146 |
|
|
|
1147 |
|
|
when ALU_MUL => -- Stage 1 of 2 {R1:R0} = R0 * Rn : Flags Z
|
1148 |
|
|
Regfile(0) <= Mult(7 downto 0);
|
1149 |
|
|
Regfile(1) <= Mult(15 downto 8);
|
1150 |
|
|
Flags(FL_ZERO) <= nor_reduce(Mult);
|
1151 |
|
|
|
1152 |
|
|
when ALU_LDI => -- Rn <= Data : Flags N,Z
|
1153 |
|
|
Flags(FL_ZERO) <= nor_reduce(ALU_Ctrl.Data);
|
1154 |
|
|
Flags(FL_NEG) <= ALU_Ctrl.Data(7);
|
1155 |
|
|
Regfile(Index) <= ALU_Ctrl.Data;
|
1156 |
|
|
|
1157 |
|
|
when ALU_POP => -- Rn <= Data
|
1158 |
|
|
Regfile(Index) <= ALU_Ctrl.Data;
|
1159 |
|
|
|
1160 |
|
|
when ALU_LDX => -- R0 <= Data : Flags N,Z
|
1161 |
|
|
Flags(FL_ZERO) <= nor_reduce(ALU_Ctrl.Data);
|
1162 |
|
|
Flags(FL_NEG) <= ALU_Ctrl.Data(7);
|
1163 |
|
|
Regfile(0) <= ALU_Ctrl.Data;
|
1164 |
|
|
|
1165 |
|
|
when ALU_RFLG =>
|
1166 |
|
|
Flags <= ALU_Ctrl.Data;
|
1167 |
|
|
|
1168 |
|
|
when others =>
|
1169 |
|
|
null;
|
1170 |
|
|
end case;
|
1171 |
|
|
|
1172 |
|
|
end if;
|
1173 |
|
|
end process;
|
1174 |
|
|
|
1175 |
|
|
end architecture;
|