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Change-Id: I25e1b337211032bb572351f8a02d3b05013330ea
This commit is contained in:
David Banks
2021-06-10 11:16:20 +01:00
parent 791ed43bae
commit 9c1181b5e1
1 changed files with 97 additions and 97 deletions
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194
cpu_65c02.v
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@@ -1,22 +1,22 @@
/*
* verilog model of 65C02 CPU.
*
* Based on original 6502 "Arlet 6502 Core" by Arlet Ottens
*
* Based on original 6502 "Arlet 6502 Core" by Arlet Ottens
*
* (C) Arlet Ottens, <arlet@c-scape.nl>
*
* Feel free to use this code in any project (commercial or not), as long as you
* keep this message, and the copyright notice. This code is provided "as is",
* keep this message, and the copyright notice. This code is provided "as is",
* without any warranties of any kind.
*
*
* Support for 65C02 instructions and addressing modes by David Banks and Ed Spittles
*
* (C) 2016 David Banks and Ed Spittles
*
*
* Feel free to use this code in any project (commercial or not), as long as you
* keep this message, and the copyright notice. This code is provided "as is",
* keep this message, and the copyright notice. This code is provided "as is",
* without any warranties of any kind.
*
*
*/
/*
@@ -32,7 +32,7 @@
* Two things were needed to correctly implement 65C02 NOPs
* 1. Ensure the microcode state machine uses an appropriate addressing mode for the opcode length
* 2. Ensure there are no side-effects (e.g. register updates, memory stores, etc)
*
*
* If IMPLEMENT_NOPS is defined, the state machine is modified accordingly.
*/
@@ -50,7 +50,7 @@
module cpu_65c02( clk, reset, AB, DI, DO, WE, IRQ, NMI, RDY );
input clk; // CPU clock
input clk; // CPU clock
input reset; // reset signal
output reg [15:0] AB; // address bus
input [7:0] DI; // data in, read bus
@@ -58,13 +58,13 @@ output [7:0] DO; // data out, write bus
output WE; // write enable
input IRQ; // interrupt request
input NMI; // non-maskable interrupt request
input RDY; // Ready signal. Pauses CPU when RDY=0
input RDY; // Ready signal. Pauses CPU when RDY=0
/*
* internal signals
*/
reg [15:0] PC; // Program Counter
reg [15:0] PC; // Program Counter
reg [7:0] ABL; // Address Bus Register LSB
reg [7:0] ABH; // Address Bus Register MSB
wire [7:0] ADD; // Adder Hold Register (registered in ALU)
@@ -73,7 +73,7 @@ reg [7:0] DIHOLD; // Hold for Data In
reg DIHOLD_valid; //
wire [7:0] DIMUX; //
reg [7:0] IRHOLD; // Hold for Instruction register
reg [7:0] IRHOLD; // Hold for Instruction register
reg IRHOLD_valid; // Valid instruction in IRHOLD
reg [7:0] AXYS[3:0]; // A, X, Y and S register file
@@ -96,11 +96,11 @@ reg [7:0] AI; // ALU Input A
reg [7:0] BI; // ALU Input B
wire [7:0] DI; // Data In
wire [7:0] IR; // Instruction register
reg [7:0] DO; // Data Out
reg [7:0] DO; // Data Out
wire [7:0] AO; // ALU output after BCD adjustment
reg WE; // Write Enable
reg CI; // Carry In
wire CO; // Carry Out
wire CO; // Carry Out
wire [7:0] PCH = PC[15:8];
wire [7:0] PCL = PC[7:0];
@@ -109,10 +109,10 @@ reg NMI_edge = 0; // captured NMI edge
reg [1:0] regsel; // Select A, X, Y or S register
wire [7:0] regfile = AXYS[regsel]; // Selected register output
parameter
parameter
SEL_A = 2'd0,
SEL_S = 2'd1,
SEL_X = 2'd2,
SEL_X = 2'd2,
SEL_Y = 2'd3;
/*
@@ -123,8 +123,8 @@ parameter
`ifdef SIM
wire [7:0] A = AXYS[SEL_A]; // Accumulator
wire [7:0] X = AXYS[SEL_X]; // X register
wire [7:0] Y = AXYS[SEL_Y]; // Y register
wire [7:0] S = AXYS[SEL_S]; // Stack pointer
wire [7:0] Y = AXYS[SEL_Y]; // Y register
wire [7:0] S = AXYS[SEL_S]; // Stack pointer
`endif
wire [7:0] P = { N, V, 2'b11, D, I, Z, C };
@@ -140,15 +140,15 @@ reg [5:0] state;
*/
reg PC_inc; // Increment PC
reg [15:0] PC_temp; // intermediate value of PC
reg [15:0] PC_temp; // intermediate value of PC
reg [1:0] src_reg; // source register index
reg [1:0] dst_reg; // destination register index
reg index_y; // if set, then Y is index reg rather than X
reg index_y; // if set, then Y is index reg rather than X
reg load_reg; // loading a register (A, X, Y, S) in this instruction
reg inc; // increment
reg write_back; // set if memory is read/modified/written
reg write_back; // set if memory is read/modified/written
reg load_only; // LDA/LDX/LDY instruction
reg store; // doing store (STA/STX/STY)
reg adc_sbc; // doing ADC/SBC
@@ -158,14 +158,14 @@ reg rotate; // doing rotate (no shift)
reg backwards; // backwards branch
reg cond_true; // branch condition is true
reg [3:0] cond_code; // condition code bits from instruction
reg shift_right; // Instruction ALU shift/rotate right
reg shift_right; // Instruction ALU shift/rotate right
reg alu_shift_right; // Current cycle shift right enable
reg [3:0] op; // Main ALU operation for instruction
reg [3:0] alu_op; // Current cycle ALU operation
reg adc_bcd; // ALU should do BCD style carry
reg [3:0] alu_op; // Current cycle ALU operation
reg adc_bcd; // ALU should do BCD style carry
reg adj_bcd; // results should be BCD adjusted
/*
/*
* some flip flops to remember we're doing special instructions. These
* get loaded at the DECODE state, and used later
*/
@@ -175,14 +175,14 @@ reg txb_ins; // doing TSB/TRB instruction
reg bit_ins; // doing BIT instruction
reg bit_ins_nv; // doing BIT instruction that will update the n and v flags (i.e. not BIT imm)
reg plp; // doing PLP instruction
reg php; // doing PHP instruction
reg php; // doing PHP instruction
reg clc; // clear carry
reg sec; // set carry
reg cld; // clear decimal
reg sed; // set decimal
reg cli; // clear interrupt
reg sei; // set interrupt
reg clv; // clear overflow
reg clv; // clear overflow
reg brk; // doing BRK
reg res; // in reset
@@ -204,17 +204,17 @@ parameter
* Microcode state machine. Basically, every addressing mode has its own
* path through the state machine. Additional information, such as the
* operation, source and destination registers are decoded in parallel, and
* kept in separate flops.
* kept in separate flops.
*/
parameter
ABS0 = 6'd0, // ABS - fetch LSB
parameter
ABS0 = 6'd0, // ABS - fetch LSB
ABS1 = 6'd1, // ABS - fetch MSB
ABSX0 = 6'd2, // ABS, X - fetch LSB and send to ALU (+X)
ABSX1 = 6'd3, // ABS, X - fetch MSB and send to ALU (+Carry)
ABSX2 = 6'd4, // ABS, X - Wait for ALU (only if needed)
BRA0 = 6'd5, // Branch - fetch offset and send to ALU (+PC[7:0])
BRA1 = 6'd6, // Branch - fetch opcode, and send PC[15:8] to ALU
BRA1 = 6'd6, // Branch - fetch opcode, and send PC[15:8] to ALU
BRA2 = 6'd7, // Branch - fetch opcode (if page boundary crossed)
BRK0 = 6'd8, // BRK/IRQ - push PCH, send S to ALU (-1)
BRK1 = 6'd9, // BRK/IRQ - push PCL, send S to ALU (-1)
@@ -225,9 +225,9 @@ parameter
INDX0 = 6'd14, // (ZP,X) - fetch ZP address, and send to ALU (+X)
INDX1 = 6'd15, // (ZP,X) - fetch LSB at ZP+X, calculate ZP+X+1
INDX2 = 6'd16, // (ZP,X) - fetch MSB at ZP+X+1
INDX3 = 6'd17, // (ZP,X) - fetch data
INDX3 = 6'd17, // (ZP,X) - fetch data
INDY0 = 6'd18, // (ZP),Y - fetch ZP address, and send ZP to ALU (+1)
INDY1 = 6'd19, // (ZP),Y - fetch at ZP+1, and send LSB to ALU (+Y)
INDY1 = 6'd19, // (ZP),Y - fetch at ZP+1, and send LSB to ALU (+Y)
INDY2 = 6'd20, // (ZP),Y - fetch data, and send MSB to ALU (+Carry)
INDY3 = 6'd21, // (ZP),Y) - fetch data (if page boundary crossed)
JMP0 = 6'd22, // JMP - fetch PCL and hold
@@ -246,15 +246,15 @@ parameter
READ = 6'd35, // Read memory for read/modify/write (INC, DEC, shift)
REG = 6'd36, // Read register for reg-reg transfers
RTI0 = 6'd37, // RTI - send S to ALU (+1)
RTI1 = 6'd38, // RTI - read P from stack
RTI1 = 6'd38, // RTI - read P from stack
RTI2 = 6'd39, // RTI - read PCL from stack
RTI3 = 6'd40, // RTI - read PCH from stack
RTI4 = 6'd41, // RTI - read PCH from stack
RTS0 = 6'd42, // RTS - send S to ALU (+1)
RTS1 = 6'd43, // RTS - read PCL from stack
RTS2 = 6'd44, // RTS - write PCL to ALU, read PCH
RTS1 = 6'd43, // RTS - read PCL from stack
RTS2 = 6'd44, // RTS - write PCL to ALU, read PCH
RTS3 = 6'd45, // RTS - load PC and increment
WRITE = 6'd46, // Write memory for read/modify/write
WRITE = 6'd46, // Write memory for read/modify/write
ZP0 = 6'd47, // Z-page - fetch ZP address
ZPX0 = 6'd48, // ZP, X - fetch ZP, and send to ALU (+X)
ZPX1 = 6'd49, // ZP, X - load from memory
@@ -326,7 +326,7 @@ always @*
JMPIX0: statename = "JMPIX0";
JMPIX1: statename = "JMPIX1";
JMPIX2: statename = "JMPIX2";
endcase
//always @( PC )
@@ -352,15 +352,15 @@ always @*
JMPI1,
JMPIX1,
JSR3,
RTS3,
RTS3,
RTI4: PC_temp = { DIMUX, ADD };
BRA1: PC_temp = { ABH, ADD };
JMPIX2,
BRA2: PC_temp = { ADD, PCL };
BRK2: PC_temp = res ? 16'hfffc :
BRK2: PC_temp = res ? 16'hfffc :
NMI_edge ? 16'hfffa : 16'hfffe;
default: PC_temp = PC;
@@ -396,15 +396,15 @@ always @*
default: PC_inc = 0;
endcase
/*
/*
* Set new PC
*/
always @(posedge clk)
always @(posedge clk)
if( RDY )
PC <= PC_temp + PC_inc;
/*
* Address Generator
* Address Generator
*/
parameter
@@ -444,7 +444,7 @@ always @*
RTI2,
RTI3,
BRK2: AB = { STACKPAGE, ADD };
INDY1,
INDX1,
ZPX1,
@@ -466,7 +466,7 @@ always @*
* source of the address, such as the ALU or DI.
*/
always @(posedge clk)
if( state != PUSH0 && state != PUSH1 && RDY &&
if( state != PUSH0 && state != PUSH1 && RDY &&
state != PULL0 && state != PULL1 && state != PULL2 )
begin
ABL <= AB[7:0];
@@ -474,7 +474,7 @@ always @(posedge clk)
end
/*
* Data Out MUX
* Data Out MUX
*/
always @*
case( state )
@@ -529,8 +529,8 @@ always @*
case( state )
DECODE: write_register = load_reg & ~plp;
PULL1,
RTS2,
PULL1,
RTS2,
RTI3,
BRK3,
JSR0,
@@ -590,7 +590,7 @@ assign AN1 = AN;
assign AZ1 = AZ;
`endif
/*
* write to a register. Usually this is the (BCD corrected) output of the
* ALU, but in case of the JSR0 we use the S register to temporarily store
@@ -603,10 +603,10 @@ always @(posedge clk)
/*
* register select logic. This determines which of the A, X, Y or
* S registers will be accessed.
* S registers will be accessed.
*/
always @*
always @*
case( state )
INDY1,
INDX0,
@@ -615,7 +615,7 @@ always @*
ABSX0 : regsel = index_y ? SEL_Y : SEL_X;
DECODE : regsel = dst_reg;
DECODE : regsel = dst_reg;
BRK0,
BRK3,
@@ -628,8 +628,8 @@ always @*
RTI3,
RTS0,
RTS2 : regsel = SEL_S;
default: regsel = src_reg;
default: regsel = src_reg;
endcase
/*
@@ -659,10 +659,10 @@ always @*
case( state )
READ: alu_op = op;
BRA1: alu_op = backwards ? OP_SUB : OP_ADD;
BRA1: alu_op = backwards ? OP_SUB : OP_ADD;
FETCH,
REG : alu_op = op;
REG : alu_op = op;
DECODE,
ABS1: alu_op = 1'bx;
@@ -688,15 +688,15 @@ always @*
alu_shift_right = 0;
/*
* Sign extend branch offset.
* Sign extend branch offset.
*/
always @(posedge clk)
if( RDY )
backwards <= DIMUX[7];
/*
* ALU A Input MUX
/*
* ALU A Input MUX
*/
always @*
@@ -727,7 +727,7 @@ always @*
BRA0,
READ: AI = DIMUX;
BRA1: AI = ABH; // don't use PCH in case we're
BRA1: AI = ABH; // don't use PCH in case we're
FETCH: AI = load_only ? 0 : regfile;
@@ -757,7 +757,7 @@ always @*
BRK0,
BRK1,
BRK2,
PUSH0,
PUSH0,
PUSH1,
PULL0,
RTS0: BI = 8'h00;
@@ -790,8 +790,8 @@ always @*
REG: CI = rotate ? C :
shift ? 0 : inc;
FETCH: CI = rotate ? C :
compare ? 1 :
FETCH: CI = rotate ? C :
compare ? 1 :
(shift | load_only) ? 0 : C;
PULL0,
@@ -801,7 +801,7 @@ always @*
RTS0,
RTS1,
INDY0,
INDX1: CI = 1;
INDX1: CI = 1;
default: CI = 0;
endcase
@@ -815,7 +815,7 @@ always @*
* Update C flag when doing ADC/SBC, shift/rotate, compare
*/
always @(posedge clk )
if( shift && state == WRITE )
if( shift && state == WRITE )
C <= CO;
else if( state == RTI2 )
C <= DIMUX[0];
@@ -832,15 +832,15 @@ always @(posedge clk )
/*
* Special Z flag got TRB/TSB
*/
always @(posedge clk)
*/
always @(posedge clk)
AZ2 <= ~|(AI & regfile);
/*
* Update Z, N flags when writing A, X, Y, Memory, or when doing compare
*/
always @(posedge clk)
always @(posedge clk)
if( state == WRITE)
Z <= txb_ins ? AZ2 : AZ1;
else if( state == RTI2 )
@@ -883,7 +883,7 @@ always @(posedge clk)
/*
* Update D flag
*/
always @(posedge clk )
always @(posedge clk )
if( state == RTI2 )
D <= DIMUX[3];
else if( state == DECODE ) begin
@@ -896,7 +896,7 @@ always @(posedge clk )
* Update V flag
*/
always @(posedge clk )
if( state == RTI2 )
if( state == RTI2 )
V <= DIMUX[6];
else if( state == DECODE ) begin
if( adc_sbc ) V <= AV;
@@ -939,8 +939,8 @@ assign IR = (IRQ & ~I) | NMI_edge ? 8'h00 :
IRHOLD_valid ? IRHOLD : DIMUX;
//assign DIMUX = ~RDY1 ? DIHOLD : DI;
assign DIMUX = DI;
assign DIMUX = DI;
/*
* Microcode state machine
@@ -949,7 +949,7 @@ always @(posedge clk or posedge reset)
if( reset )
state <= BRK0;
else if( RDY ) case( state )
DECODE :
DECODE :
casex ( IR )
// TODO Review for simplifications as in verilog the first matching case has priority
8'b0000_0000: state <= BRK0;
@@ -957,23 +957,23 @@ always @(posedge clk or posedge reset)
8'b0010_1100: state <= ABS0; // BIT abs
8'b1001_1100: state <= ABS0; // STZ abs
8'b000x_1100: state <= ABS0; // TSB/TRB
8'b0100_0000: state <= RTI0; //
8'b0100_0000: state <= RTI0; //
8'b0100_1100: state <= JMP0;
8'b0110_0000: state <= RTS0;
8'b0110_1100: state <= JMPI0;
8'b0111_1100: state <= JMPIX0;
`ifdef IMPLEMENT_NOPS
`ifdef IMPLEMENT_NOPS
8'bxxxx_xx11: state <= REG; // (NOP1: 3/7/B/F column)
8'bxxx0_0010: state <= FETCH; // (NOP2: 2 column, 4 column handled correctly below)
8'bx1x1_1100: state <= ABS0; // (NOP3: C column)
`endif
8'b0x00_1000: state <= PUSH0;
8'b0x10_1000: state <= PULL0;
8'b0xx1_1000: state <= REG; // CLC, SEC, CLI, SEI
8'b0xx1_1000: state <= REG; // CLC, SEC, CLI, SEI
8'b11x0_00x0: state <= FETCH; // IMM
8'b1x10_00x0: state <= FETCH; // IMM
8'b1xx0_1100: state <= ABS0; // X/Y abs
8'b1xxx_1000: state <= REG; // DEY, TYA, ...
8'b1xxx_1000: state <= REG; // DEY, TYA, ...
8'bxxx0_0001: state <= INDX0;
8'bxxx1_0010: state <= IND0; // (ZP) odd 2 column
8'b000x_0100: state <= ZP0; // TSB/TRB
@@ -1028,18 +1028,18 @@ always @(posedge clk or posedge reset)
FETCH : state <= DECODE;
REG : state <= DECODE;
PUSH0 : state <= PUSH1;
PUSH1 : state <= DECODE;
PULL0 : state <= PULL1;
PULL1 : state <= PULL2;
PULL1 : state <= PULL2;
PULL2 : state <= DECODE;
JSR0 : state <= JSR1;
JSR1 : state <= JSR2;
JSR2 : state <= JSR3;
JSR3 : state <= FETCH;
JSR3 : state <= FETCH;
RTI0 : state <= RTI1;
RTI1 : state <= RTI2;
@@ -1057,7 +1057,7 @@ always @(posedge clk or posedge reset)
BRA2 : state <= DECODE;
JMP0 : state <= JMP1;
JMP1 : state <= DECODE;
JMP1 : state <= DECODE;
JMPI0 : state <= JMPI1;
JMPI1 : state <= JMP0;
@@ -1087,7 +1087,7 @@ always @(posedge clk)
8'b0xxx_1010, // ASLA, INCA, ROLA, DECA, LSRA, PHY, RORA, PLY
8'b0xxx_xx01, // ORA, AND, EOR, ADC
8'b100x_10x0, // DEY, TYA, TXA, TXS
8'b1010_xxx0, // LDA/LDX/LDY
8'b1010_xxx0, // LDA/LDX/LDY
8'b1011_1010, // TSX
8'b1011_x1x0, // LDX/LDY
8'b1100_1010, // DEX
@@ -1127,15 +1127,15 @@ always @(posedge clk)
always @(posedge clk)
if( state == DECODE && RDY )
casex( IR )
8'b1011_1010: // TSX
src_reg <= SEL_S;
8'b1011_1010: // TSX
src_reg <= SEL_S;
8'b100x_x110, // STX
8'b100x_1x10, // TXA, TXS
8'b1110_xx00, // INX, CPX
8'b1101_1010, // PHX
8'b1100_1010: // DEX
src_reg <= SEL_X;
src_reg <= SEL_X;
8'b100x_x100, // STY
8'b1001_1000, // TYA
@@ -1147,7 +1147,7 @@ always @(posedge clk)
default: src_reg <= SEL_A;
endcase
always @(posedge clk)
always @(posedge clk)
if( state == DECODE && RDY )
casex( IR )
8'bxxx1_0001, // INDY
@@ -1178,7 +1178,7 @@ always @(posedge clk )
casex( IR ) // DMB: Checked for 65C02 NOP collisions
8'b0xxx_x110, // ASL, ROL, LSR, ROR
8'b000x_x100, // TSB/TRB
8'b11xx_x110: // DEC/INC
8'b11xx_x110: // DEC/INC
write_back <= 1;
default: write_back <= 0;
@@ -1197,7 +1197,7 @@ always @(posedge clk )
if( state == DECODE && RDY )
casex( IR )
8'b0001_1010, // INCA
8'b111x_x110, // INC
8'b111x_x110, // INC
8'b11x0_1000: // INX, INY
inc <= 1;
@@ -1240,7 +1240,7 @@ always @(posedge clk )
8'b1101_0010, // CMP (zp)
8'b11x0_0x00, // CPX, CPY (imm/zp)
8'b11x0_1100, // CPX, CPY (abs)
8'b110x_xx01: // CMP
8'b110x_xx01: // CMP
compare <= 1;
default: compare <= 0;
@@ -1253,17 +1253,17 @@ always @(posedge clk )
8'b01xx_1x10: // ROR, LSR
shift_right <= 1;
default: shift_right <= 0;
default: shift_right <= 0;
endcase
always @(posedge clk )
if( state == DECODE && RDY )
casex( IR )
8'b0x10_1010, // ROL A, ROR A
8'b0x1x_x110: // ROR, ROL
8'b0x1x_x110: // ROR, ROL
rotate <= 1;
default: rotate <= 0;
default: rotate <= 0;
endcase
always @(posedge clk )
@@ -1290,8 +1290,8 @@ always @(posedge clk )
8'b11x1_0010, // CMP, SBC (zp)
8'b0011_1010, // DEC A
8'b1000_1000, // DEY
8'b1100_1010, // DEX
8'b110x_x110, // DEC
8'b1100_1010, // DEX
8'b110x_x110, // DEC
8'b11xx_xx01, // CMP, SBC
8'b11x0_0x00, // CPX, CPY (imm, zpg)
8'b11x0_1100: op <= OP_SUB;
@@ -1301,8 +1301,8 @@ always @(posedge clk )
8'b010x_xx01, // EOR
8'b00xx_xx01: // ORA, AND
op <= { 2'b11, IR[6:5] };
default: op <= OP_ADD;
default: op <= OP_ADD;
endcase
always @(posedge clk )