-`define REG_A 0
-`define REG_B 1
-`define REG_C 2
-`define REG_D 3
-`define REG_E 4
-`define REG_F 5
-`define REG_H 6
-`define REG_L 7
-`define REG_SPH 8
-`define REG_SPL 9
-`define REG_PCH 10
-`define REG_PCL 11
+`define REG_A 0
+`define REG_B 1
+`define REG_C 2
+`define REG_D 3
+`define REG_E 4
+`define REG_F 5
+`define REG_H 6
+`define REG_L 7
+`define REG_SPH 8
+`define REG_SPL 9
+`define REG_PCH 10
+`define REG_PCL 11
-`define FLAG_Z 8'b10000000
-`define FLAG_N 8'b01000000
-`define FLAG_H 8'b00100000
-`define FLAG_C 8'b00010000
+`define _A registers[`REG_A]
+`define _B registers[`REG_B]
+`define _C registers[`REG_C]
+`define _D registers[`REG_D]
+`define _E registers[`REG_E]
+`define _F registers[`REG_F]
+`define _H registers[`REG_H]
+`define _L registers[`REG_L]
+`define _SPH registers[`REG_SPH]
+`define _SPL registers[`REG_SPL]
+`define _PCH registers[`REG_PCH]
+`define _PCL registers[`REG_PCL]
+`define _AF {`_A, `_F}
+`define _BC {`_B, `_C}
+`define _DE {`_D, `_E}
+`define _HL {`_H, `_L}
+`define _SP {`_SPH, `_SPL}
+`define _PC {`_PCH, `_PCL}
-`define STATE_FETCH 2'h0
-`define STATE_DECODE 2'h1
+`define FLAG_Z 8'b10000000
+`define FLAG_N 8'b01000000
+`define FLAG_H 8'b00100000
+`define FLAG_C 8'b00010000
+
+`define STATE_FETCH 2'h0
+`define STATE_DECODE 2'h1
`define STATE_EXECUTE 2'h2
`define STATE_WRITEBACK 2'h3
`define INSN_LD_reg_imm8 8'b00xxx110
-`define INSN_HALT 8'b01110110
+`define INSN_HALT 8'b01110110
`define INSN_LD_HL_reg 8'b01110xxx
`define INSN_LD_reg_HL 8'b01xxx110
`define INSN_LD_reg_reg 8'b01xxxxxx
`define INSN_LD_SP_HL 8'b11111001
`define INSN_PUSH_reg 8'b11xx0101
`define INSN_POP_reg 8'b11xx0001
+`define INSN_LDH_AC 8'b111x0010 // Either LDH A,(C) or LDH (C),A
+`define INSN_LDx_AHL 8'b001xx010 // LDD/LDI A,(HL) / (HL),A
+`define INSN_ALU8 8'b10xxxxxx // 10 xxx yyy
+`define INSN_NOP 8'b00000000
+`define INSN_RST 8'b11xxx111
+`define INSN_RET 8'b110x1001 // 1 = RETI, 0 = RET
+`define INSN_RETCC 8'b110xx000
+`define INSN_CALL 8'b11001101
+`define INSN_CALLCC 8'b110xx100 // Not that call/cc.
+`define INSN_JP_imm 8'b11000011
+`define INSN_JPCC_imm 8'b110xx010
+`define INSN_ALU_A 8'b00xxx111
+`define INSN_JP_HL 8'b11101001
+`define INSN_JR_imm 8'b00011000
+`define INSN_JRCC_imm 8'b001xx000
+`define INSN_INCDEC16 8'b00xxx011
+`define INSN_VOP_INTR 8'b11111100 // 0xFC is grabbed by the fetch if there is an interrupt pending.
+`define INSN_DI 8'b11110011
+`define INSN_EI 8'b11111011
+
+`define INSN_cc_NZ 2'b00
+`define INSN_cc_Z 2'b01
+`define INSN_cc_NC 2'b10
+`define INSN_cc_C 2'b11
+
`define INSN_reg_A 3'b111
`define INSN_reg_B 3'b000
`define INSN_reg_C 3'b001
`define INSN_reg_E 3'b011
`define INSN_reg_H 3'b100
`define INSN_reg_L 3'b101
-`define INSN_reg_dHL 3'b110
-`define INSN_reg16_BC 2'b00
-`define INSN_reg16_DE 2'b01
-`define INSN_reg16_HL 2'b10
-`define INSN_reg16_SP 2'b11
-`define INSN_stack_AF 2'b11
-`define INSN_stack_BC 2'b00
-`define INSN_stack_DE 2'b01
-`define INSN_stack_HL 2'b10
+`define INSN_reg_dHL 3'b110
+`define INSN_reg16_BC 2'b00
+`define INSN_reg16_DE 2'b01
+`define INSN_reg16_HL 2'b10
+`define INSN_reg16_SP 2'b11
+`define INSN_stack_AF 2'b11
+`define INSN_stack_BC 2'b00
+`define INSN_stack_DE 2'b01
+`define INSN_stack_HL 2'b10
+`define INSN_alu_ADD 3'b000
+`define INSN_alu_ADC 3'b001
+`define INSN_alu_SUB 3'b010
+`define INSN_alu_SBC 3'b011
+`define INSN_alu_AND 3'b100
+`define INSN_alu_XOR 3'b101
+`define INSN_alu_OR 3'b110
+`define INSN_alu_CP 3'b111 // Oh lawd, is dat some CP?
+`define INSN_alu_RLCA 3'b000
+`define INSN_alu_RRCA 3'b001
+`define INSN_alu_RLA 3'b010
+`define INSN_alu_RRA 3'b011
+`define INSN_alu_DAA 3'b100
+`define INSN_alu_CPL 3'b101
+`define INSN_alu_SCF 3'b110
+`define INSN_alu_CCF 3'b111
+
+`define EXEC_INC_PC `_PC <= `_PC + 1;
+`define EXEC_NEXTADDR_PCINC address <= `_PC + 1;
+`define EXEC_NEWCYCLE begin newcycle <= 1; rd <= 1; wr <= 0; end
+`define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end end
+`define EXEC_READ(ad) begin address <= (ad); rd <= 1; end end
+
module GBZ80Core(
input clk,
output reg [15:0] busaddress, /* BUS_* is latched on STATE_FETCH. */
inout [7:0] busdata,
- output reg buswr, output reg busrd);
+ output reg buswr, output reg busrd,
+ input irq, input [7:0] jaddr);
- reg [1:0] state = 0; /* State within this bus cycle (see STATE_*). */
- reg [2:0] cycle = 0; /* Cycle for instructions. */
+ reg [1:0] state; /* State within this bus cycle (see STATE_*). */
+ reg [2:0] cycle; /* Cycle for instructions. */
reg [7:0] registers[11:0];
reg [7:0] opcode; /* Opcode from the current machine cycle. */
reg [7:0] rdata, wdata; /* Read data from this bus cycle, or write data for the next. */
- reg rd = 1, wr = 0, newcycle = 1;
+ reg rd, wr, newcycle;
- reg [7:0] tmp; /* Generic temporary reg. */
+ reg [7:0] tmp, tmp2; /* Generic temporary regs. */
reg [7:0] buswdata;
assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
+ reg ie, iedelay;
+
initial begin
- registers[ 0] = 0;
- registers[ 1] = 0;
- registers[ 2] = 0;
- registers[ 3] = 0;
- registers[ 4] = 0;
- registers[ 5] = 0;
- registers[ 6] = 0;
- registers[ 7] = 0;
- registers[ 8] = 0;
- registers[ 9] = 0;
- registers[10] = 0;
- registers[11] = 0;
+ registers[ 0] <= 0;
+ registers[ 1] <= 0;
+ registers[ 2] <= 0;
+ registers[ 3] <= 0;
+ registers[ 4] <= 0;
+ registers[ 5] <= 0;
+ registers[ 6] <= 0;
+ registers[ 7] <= 0;
+ registers[ 8] <= 0;
+ registers[ 9] <= 0;
+ registers[10] <= 0;
+ registers[11] <= 0;
+ rd <= 1;
+ wr <= 0;
+ newcycle <= 1;
+ state <= 0;
+ cycle <= 0;
+ busrd <= 0;
+ buswr <= 0;
+ busaddress <= 0;
+ ie <= 0;
+ iedelay <= 0;
+ opcode <= 0;
+ state <= `STATE_WRITEBACK;
+ cycle <= 0;
end
always @(posedge clk)
case (state)
`STATE_FETCH: begin
- if (wr)
- buswdata <= wdata;
- if (newcycle)
+ if (newcycle) begin
busaddress <= {registers[`REG_PCH], registers[`REG_PCL]};
- else
+ buswr <= 0;
+ busrd <= 1;
+ end else begin
busaddress <= address;
- buswr <= wr;
- busrd <= rd;
+ buswr <= wr;
+ busrd <= rd;
+ if (wr)
+ buswdata <= wdata;
+ end
state <= `STATE_DECODE;
end
`STATE_DECODE: begin
if (newcycle) begin
- opcode <= busdata;
+ if (ie && irq)
+ opcode <= `INSN_VOP_INTR;
+ else
+ opcode <= busdata;
rdata <= busdata;
newcycle <= 0;
cycle <= 0;
- end else
+ end else begin
if (rd) rdata <= busdata;
+ cycle <= cycle + 1;
+ end
+ if (iedelay) begin
+ ie <= 1;
+ iedelay <= 0;
+ end
buswr <= 0;
busrd <= 0;
wr <= 0;
state <= `STATE_EXECUTE;
end
`STATE_EXECUTE: begin
-`define EXEC_INC_PC \
- {registers[`REG_PCH], registers[`REG_PCL]} <= {registers[`REG_PCH], registers[`REG_PCL]} + 1
-`define EXEC_NEXTADDR_PCINC \
- address <= {registers[`REG_PCH], registers[`REG_PCL]} + 1
-`define EXEC_NEWCYCLE \
- newcycle <= 1; rd <= 1; wr <= 0
casex (opcode)
- `INSN_LD_reg_imm8: begin
- case (cycle)
- 0: begin
- `EXEC_INC_PC;
- `EXEC_NEXTADDR_PCINC;
- rd <= 1;
- end
- 1: begin
- `EXEC_INC_PC;
- if (opcode[5:3] == `INSN_reg_dHL) begin
- address <= {registers[`REG_H], registers[`REG_L]};
- wdata <= rdata;
- rd <= 0;
- wr <= 1;
- end else begin
- `EXEC_NEWCYCLE;
- end
- end
- 2: begin
- `EXEC_NEWCYCLE;
- end
- endcase
- end
- `INSN_HALT: begin
- `EXEC_NEWCYCLE;
- /* XXX Interrupts needed for HALT. */
- end
- `INSN_LD_HL_reg: begin
- case (cycle)
- 0: begin
- case (opcode[2:0])
- `INSN_reg_A: begin wdata <= registers[`REG_A]; end
- `INSN_reg_B: begin wdata <= registers[`REG_B]; end
- `INSN_reg_C: begin wdata <= registers[`REG_C]; end
- `INSN_reg_D: begin wdata <= registers[`REG_D]; end
- `INSN_reg_E: begin wdata <= registers[`REG_E]; end
- `INSN_reg_H: begin wdata <= registers[`REG_H]; end
- `INSN_reg_L: begin wdata <= registers[`REG_L]; end
- endcase
- address <= {registers[`REG_H], registers[`REG_L]};
- wr <= 1; rd <= 0;
- end
- 1: begin
- `EXEC_INC_PC;
- `EXEC_NEWCYCLE;
- end
- endcase
- end
- `INSN_LD_reg_HL: begin
- case(cycle)
- 0: begin
- address <= {registers[`REG_H], registers[`REG_L]};
- rd <= 1;
- end
- 1: begin
- tmp <= rdata;
- `EXEC_INC_PC;
- `EXEC_NEWCYCLE;
- end
- endcase
- end
- `INSN_LD_reg_reg: begin
- `EXEC_INC_PC;
- `EXEC_NEWCYCLE;
- case (opcode[2:0])
- `INSN_reg_A: begin tmp <= registers[`REG_A]; end
- `INSN_reg_B: begin tmp <= registers[`REG_B]; end
- `INSN_reg_C: begin tmp <= registers[`REG_C]; end
- `INSN_reg_D: begin tmp <= registers[`REG_D]; end
- `INSN_reg_E: begin tmp <= registers[`REG_E]; end
- `INSN_reg_H: begin tmp <= registers[`REG_H]; end
- `INSN_reg_L: begin tmp <= registers[`REG_L]; end
- endcase
- end
- `INSN_LD_reg_imm16: begin
- `EXEC_INC_PC;
- case (cycle)
- 0: begin
- `EXEC_NEXTADDR_PCINC;
- rd <= 1;
- end
- 1: begin
- `EXEC_NEXTADDR_PCINC;
- rd <= 1;
- end
- 2: begin `EXEC_NEWCYCLE; end
- endcase
- end
- `INSN_LD_SP_HL: begin
- case (cycle)
- 0: begin
- tmp <= registers[`REG_H];
- end
- 1: begin
- `EXEC_NEWCYCLE;
- `EXEC_INC_PC;
- tmp <= registers[`REG_L];
- end
- endcase
- end
- `INSN_PUSH_reg: begin /* PUSH is 16 cycles! */
- case (cycle)
- 0: begin
- wr <= 1;
- address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
- case (opcode[5:4])
- `INSN_stack_AF: wdata <= registers[`REG_A];
- `INSN_stack_BC: wdata <= registers[`REG_B];
- `INSN_stack_DE: wdata <= registers[`REG_D];
- `INSN_stack_HL: wdata <= registers[`REG_H];
- endcase
- end
- 1: begin
- wr <= 1;
- address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
- case (opcode[5:4])
- `INSN_stack_AF: wdata <= registers[`REG_F];
- `INSN_stack_BC: wdata <= registers[`REG_C];
- `INSN_stack_DE: wdata <= registers[`REG_E];
- `INSN_stack_HL: wdata <= registers[`REG_L];
- endcase
- end
- 2: begin /* TWIDDLE OUR FUCKING THUMBS! */ end
- 3: begin
- `EXEC_NEWCYCLE;
- `EXEC_INC_PC;
- end
- endcase
- end
- `INSN_POP_reg: begin /* POP is 12 cycles! */
- case (cycle)
- 0: begin
- rd <= 1;
- address <= {registers[`REG_SPH],registers[`REG_SPL]};
- end
- 1: begin
- rd <= 1;
- address <= {registers[`REG_SPH],registers[`REG_SPL]};
- end
- 2: begin
- `EXEC_NEWCYCLE;
- `EXEC_INC_PC;
- end
- endcase
- end
+ `define EXECUTE
+ `include "allinsns.v"
+ `undef EXECUTE
default:
$stop;
endcase
end
`STATE_WRITEBACK: begin
casex (opcode)
- `INSN_LD_reg_imm8:
- case (cycle)
- 0: cycle <= 1;
- 1: case (opcode[5:3])
- `INSN_reg_A: begin registers[`REG_A] <= rdata; cycle <= 0; end
- `INSN_reg_B: begin registers[`REG_B] <= rdata; cycle <= 0; end
- `INSN_reg_C: begin registers[`REG_C] <= rdata; cycle <= 0; end
- `INSN_reg_D: begin registers[`REG_D] <= rdata; cycle <= 0; end
- `INSN_reg_E: begin registers[`REG_E] <= rdata; cycle <= 0; end
- `INSN_reg_H: begin registers[`REG_H] <= rdata; cycle <= 0; end
- `INSN_reg_L: begin registers[`REG_L] <= rdata; cycle <= 0; end
- `INSN_reg_dHL: cycle <= 2;
- endcase
- 2: cycle <= 0;
- endcase
- `INSN_HALT: begin
- /* Nothing needs happen here. */
- /* XXX Interrupts needed for HALT. */
- end
- `INSN_LD_HL_reg: begin
- case (cycle)
- 0: cycle <= 1;
- 1: cycle <= 0;
- endcase
- end
- `INSN_LD_reg_HL: begin
- case (cycle)
- 0: cycle <= 1;
- 1: begin
- case (opcode[5:3])
- `INSN_reg_A: begin registers[`REG_A] <= tmp; end
- `INSN_reg_B: begin registers[`REG_B] <= tmp; end
- `INSN_reg_C: begin registers[`REG_C] <= tmp; end
- `INSN_reg_D: begin registers[`REG_D] <= tmp; end
- `INSN_reg_E: begin registers[`REG_E] <= tmp; end
- `INSN_reg_H: begin registers[`REG_H] <= tmp; end
- `INSN_reg_L: begin registers[`REG_L] <= tmp; end
- endcase
- cycle <= 0;
- end
- endcase
- end
- `INSN_LD_reg_reg: begin
- case (opcode[5:3])
- `INSN_reg_A: begin registers[`REG_A] <= tmp; end
- `INSN_reg_B: begin registers[`REG_B] <= tmp; end
- `INSN_reg_C: begin registers[`REG_C] <= tmp; end
- `INSN_reg_D: begin registers[`REG_D] <= tmp; end
- `INSN_reg_E: begin registers[`REG_E] <= tmp; end
- `INSN_reg_H: begin registers[`REG_H] <= tmp; end
- `INSN_reg_L: begin registers[`REG_L] <= tmp; end
- endcase
- end
- `INSN_LD_reg_imm16: begin
- case (cycle)
- 0: cycle <= 1;
- 1: begin
- case (opcode[5:4])
- `INSN_reg16_BC: registers[`REG_C] <= rdata;
- `INSN_reg16_DE: registers[`REG_E] <= rdata;
- `INSN_reg16_HL: registers[`REG_L] <= rdata;
- `INSN_reg16_SP: registers[`REG_SPL] <= rdata;
- endcase
- cycle <= 2;
- end
- 2: begin
- case (opcode[5:4])
- `INSN_reg16_BC: registers[`REG_B] <= rdata;
- `INSN_reg16_DE: registers[`REG_D] <= rdata;
- `INSN_reg16_HL: registers[`REG_H] <= rdata;
- `INSN_reg16_SP: registers[`REG_SPH] <= rdata;
- endcase
- cycle <= 0;
- end
- endcase
- end
- `INSN_LD_SP_HL: begin
- case (cycle)
- 0: begin
- cycle <= 1;
- registers[`REG_SPH] <= tmp;
- end
- 1: begin
- cycle <= 0;
- registers[`REG_SPL] <= tmp;
- end
- endcase
- end
- `INSN_PUSH_reg: begin /* PUSH is 16 cycles! */
- case (cycle)
- 0: begin
- {registers[`REG_SPH],registers[`REG_SPL]} =
- {registers[`REG_SPH],registers[`REG_SPL]} - 1;
- cycle <= 1;
- end
- 1: begin
- {registers[`REG_SPH],registers[`REG_SPL]} =
- {registers[`REG_SPH],registers[`REG_SPL]} - 1;
- cycle <= 2;
- end
- 2: cycle <= 3;
- 3: cycle <= 0;
- endcase
- end
- `INSN_POP_reg: begin /* POP is 12 cycles! */
- case (cycle)
- 0: begin
- cycle <= 1;
- {registers[`REG_SPH],registers[`REG_SPL]} =
- {registers[`REG_SPH],registers[`REG_SPL]} + 1;
- end
- 1: begin
- case (opcode[5:4])
- `INSN_stack_AF: registers[`REG_F] <= rdata;
- `INSN_stack_BC: registers[`REG_C] <= rdata;
- `INSN_stack_DE: registers[`REG_E] <= rdata;
- `INSN_stack_HL: registers[`REG_L] <= rdata;
- endcase
- {registers[`REG_SPH],registers[`REG_SPL]} =
- {registers[`REG_SPH],registers[`REG_SPL]} + 1;
- cycle <= 2;
- end
- 2: begin
- case (opcode[5:4])
- `INSN_stack_AF: registers[`REG_A] <= rdata;
- `INSN_stack_BC: registers[`REG_B] <= rdata;
- `INSN_stack_DE: registers[`REG_D] <= rdata;
- `INSN_stack_HL: registers[`REG_H] <= rdata;
- endcase
- cycle <= 0;
- end
- endcase
- end
+ `define WRITEBACK
+ `include "allinsns.v"
+ `undef WRITEBACK
+ default:
+ $stop;
endcase
state <= `STATE_FETCH;
end
endcase
endmodule
-
-`timescale 1ns / 1ps
-module TestBench();
- reg clk = 0;
- wire [15:0] addr;
- wire [7:0] data;
- wire wr, rd;
- reg [7:0] rom [2047:0];
-
- initial $readmemh("rom.hex", rom);
- always #10 clk <= ~clk;
- GBZ80Core core(
- .clk(clk),
- .busaddress(addr),
- .busdata(data),
- .buswr(wr),
- .busrd(rd));
- assign data = rd ? rom[addr] : 8'bzzzzzzzz;
-endmodule
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