`define STATE_WRITEBACK 2'h3
`define INSN_LD_reg_imm8 8'b00xxx110
-`define INSN_imm8_reg_A 3'b111
-`define INSN_imm8_reg_B 3'b000
-`define INSN_imm8_reg_C 3'b001
-`define INSN_imm8_reg_D 3'b010
-`define INSN_imm8_reg_E 3'b011
-`define INSN_imm8_reg_H 3'b100
-`define INSN_imm8_reg_L 3'b101
-`define INSN_imm8_reg_dHL 3'b110
+`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_reg_A 3'b111
+`define INSN_reg_B 3'b000
+`define INSN_reg_C 3'b001
+`define INSN_reg_D 3'b010
+`define INSN_reg_E 3'b011
+`define INSN_reg_H 3'b100
+`define INSN_reg_L 3'b101
+`define INSN_reg_dHL 3'b110
module GBZ80Core(
input clk,
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 [7:0] tmp; /* Generic temporary reg. */
+
reg [7:0] buswdata;
assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
if (newcycle) begin
opcode <= busdata;
rdata <= busdata;
+ newcycle <= 0;
cycle <= 0;
end else
if (rd) rdata <= busdata;
0: begin
`EXEC_INC_PC;
`EXEC_NEXTADDR_PCINC;
- newcycle <= 0;
rd <= 1;
end
1: begin
`EXEC_INC_PC;
- if (opcode[5:3] == `INSN_imm8_reg_dHL) begin
+ if (opcode[5:3] == `INSN_reg_dHL) begin
address <= {registers[`REG_H], registers[`REG_L]};
wdata <= rdata;
rd <= 0;
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]};
+ wr <= 0; 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
endcase
state <= `STATE_WRITEBACK;
end
case (cycle)
0: cycle <= 1;
1: case (opcode[5:3])
- `INSN_imm8_reg_A: begin registers[`REG_A] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_B: begin registers[`REG_B] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_C: begin registers[`REG_C] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_D: begin registers[`REG_D] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_E: begin registers[`REG_E] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_H: begin registers[`REG_H] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_L: begin registers[`REG_L] <= rdata; cycle <= 0; end
- `INSN_imm8_reg_dHL: cycle <= 2;
+ `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
endcase
state <= `STATE_FETCH;
end
git.joshuawise.com / fpgaboy.git / blobdiff