`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_CALL 8'b11001101
`define INSN_reg_A 3'b111
`define INSN_reg_B 3'b000
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] tmp, tmp2; /* Generic temporary regs. */
reg [7:0] buswdata;
assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
+ reg ie = 0;
+
initial begin
registers[ 0] <= 0;
registers[ 1] <= 0;
registers[ 9] <= 0;
registers[10] <= 0;
registers[11] <= 0;
+ ie <= 0;
+ rd <= 1;
+ wr <= 0;
+ newcycle <= 1;
+ state <= 0;
+ 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
rdata <= busdata;
newcycle <= 0;
cycle <= 0;
- end else
+ end else begin
if (rd) rdata <= busdata;
+ cycle <= cycle + 1;
+ end
buswr <= 0;
busrd <= 0;
wr <= 0;
`EXEC_NEXTADDR_PCINC;
rd <= 1;
end
- 1: begin
+ 1: begin
`EXEC_INC_PC;
if (opcode[5:3] == `INSN_reg_dHL) begin
address <= {registers[`REG_H], registers[`REG_L]};
`EXEC_NEWCYCLE;
end
end
- 2: begin
+ 2: begin
`EXEC_NEWCYCLE;
end
endcase
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
+ `INSN_reg_A: wdata <= registers[`REG_A];
+ `INSN_reg_B: wdata <= registers[`REG_B];
+ `INSN_reg_C: wdata <= registers[`REG_C];
+ `INSN_reg_D: wdata <= registers[`REG_D];
+ `INSN_reg_E: wdata <= registers[`REG_E];
+ `INSN_reg_H: wdata <= registers[`REG_H];
+ `INSN_reg_L: wdata <= registers[`REG_L];
endcase
address <= {registers[`REG_H], registers[`REG_L]};
wr <= 1; rd <= 0;
end
`INSN_LD_reg_HL: begin
case(cycle)
- 0: begin
+ 0: begin
address <= {registers[`REG_H], registers[`REG_L]};
rd <= 1;
end
- 1: begin
+ 1: begin
tmp <= rdata;
`EXEC_INC_PC;
`EXEC_NEWCYCLE;
`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
+ `INSN_reg_A: tmp <= registers[`REG_A];
+ `INSN_reg_B: tmp <= registers[`REG_B];
+ `INSN_reg_C: tmp <= registers[`REG_C];
+ `INSN_reg_D: tmp <= registers[`REG_D];
+ `INSN_reg_E: tmp <= registers[`REG_E];
+ `INSN_reg_H: tmp <= registers[`REG_H];
+ `INSN_reg_L: tmp <= registers[`REG_L];
endcase
end
`INSN_LD_reg_imm16: begin
end
`INSN_PUSH_reg: begin /* PUSH is 16 cycles! */
case (cycle)
- 0: begin
+ 0: begin
wr <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
case (opcode[5:4])
`INSN_stack_HL: wdata <= registers[`REG_H];
endcase
end
- 1: begin
+ 1: begin
wr <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
case (opcode[5:4])
endcase
end
2: begin /* TWIDDLE OUR FUCKING THUMBS! */ end
- 3: begin
+ 3: begin
`EXEC_NEWCYCLE;
`EXEC_INC_PC;
end
end
`INSN_POP_reg: begin /* POP is 12 cycles! */
case (cycle)
- 0: begin
+ 0: begin
rd <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]};
end
- 1: begin
+ 1: begin
rd <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]};
end
- 2: begin
+ 2: begin
`EXEC_NEWCYCLE;
`EXEC_INC_PC;
end
wdata <= registers[`REG_A];
end
end
- 1: begin
+ 1: begin
`EXEC_NEWCYCLE;
`EXEC_INC_PC;
end
end
`INSN_LDx_AHL: begin
case (cycle)
- 0: begin
+ 0: begin
address <= {registers[`REG_H],registers[`REG_L]};
if (opcode[3]) begin // LDx A, (HL)
rd <= 1;
`EXEC_NEWCYCLE;
`EXEC_INC_PC;
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
- `INSN_reg_dHL: begin tmp <= rdata; end
+ `INSN_reg_A: tmp <= registers[`REG_A];
+ `INSN_reg_B: tmp <= registers[`REG_B];
+ `INSN_reg_C: tmp <= registers[`REG_C];
+ `INSN_reg_D: tmp <= registers[`REG_D];
+ `INSN_reg_E: tmp <= registers[`REG_E];
+ `INSN_reg_H: tmp <= registers[`REG_H];
+ `INSN_reg_L: tmp <= registers[`REG_L];
+ `INSN_reg_dHL: tmp <= rdata;
endcase
end
end
end
`INSN_RST: begin
case (cycle)
- 0: begin
+ 0: begin
+ `EXEC_INC_PC; // This goes FIRST in RST
+ end
+ 1: begin
wr <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
wdata <= registers[`REG_PCH];
end
- 1: begin
+ 2: begin
wr <= 1;
address <= {registers[`REG_SPH],registers[`REG_SPL]}-2;
wdata <= registers[`REG_PCL];
end
- 2: begin /* wee */ end
- 3: begin
+ 3: begin
`EXEC_NEWCYCLE;
{registers[`REG_PCH],registers[`REG_PCL]} <=
{10'b0,opcode[5:3],3'b0};
end
endcase
end
+ `INSN_RET: begin
+ 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]} + 1;
+ end
+ 2: begin /* twiddle thumbs */ end
+ 3: begin
+ `EXEC_NEWCYCLE;
+ // do NOT increment PC!
+ end
+ endcase
+ end
+ `INSN_CALL: begin
+ case (cycle)
+ 0: begin
+ `EXEC_INC_PC;
+ `EXEC_NEXTADDR_PCINC;
+ rd <= 1;
+ end
+ 1: begin
+ `EXEC_INC_PC;
+ `EXEC_NEXTADDR_PCINC;
+ rd <= 1;
+ end
+ 2: begin
+ `EXEC_INC_PC;
+ end
+ 3: begin
+ address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+ wdata <= registers[`REG_PCH];
+ wr <= 1;
+ end
+ 4: begin
+ address <= {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+ wdata <= registers[`REG_PCL];
+ wr <= 1;
+ end
+ 5: begin
+ `EXEC_NEWCYCLE; /* do NOT increment the PC */
+ end
+ endcase
+ end
default:
$stop;
endcase
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;
+ 0: begin end
+ 1: case (opcode[5:3])
+ `INSN_reg_A: begin registers[`REG_A] <= rdata; end
+ `INSN_reg_B: begin registers[`REG_B] <= rdata; end
+ `INSN_reg_C: begin registers[`REG_C] <= rdata; end
+ `INSN_reg_D: begin registers[`REG_D] <= rdata; end
+ `INSN_reg_E: begin registers[`REG_E] <= rdata; end
+ `INSN_reg_H: begin registers[`REG_H] <= rdata; end
+ `INSN_reg_L: begin registers[`REG_L] <= rdata; end
+ `INSN_reg_dHL: begin /* Go off to cycle 2 */ end
endcase
- 2: cycle <= 0;
+ 2: begin end
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
+ /* Nothing of interest here */
end
`INSN_LD_reg_HL: begin
case (cycle)
- 0: cycle <= 1;
+ 0: begin end
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
+ `INSN_reg_A: registers[`REG_A] <= tmp;
+ `INSN_reg_B: registers[`REG_B] <= tmp;
+ `INSN_reg_C: registers[`REG_C] <= tmp;
+ `INSN_reg_D: registers[`REG_D] <= tmp;
+ `INSN_reg_E: registers[`REG_E] <= tmp;
+ `INSN_reg_H: registers[`REG_H] <= tmp;
+ `INSN_reg_L: registers[`REG_L] <= tmp;
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
+ `INSN_reg_A: registers[`REG_A] <= tmp;
+ `INSN_reg_B: registers[`REG_B] <= tmp;
+ `INSN_reg_C: registers[`REG_C] <= tmp;
+ `INSN_reg_D: registers[`REG_D] <= tmp;
+ `INSN_reg_E: registers[`REG_E] <= tmp;
+ `INSN_reg_H: registers[`REG_H] <= tmp;
+ `INSN_reg_L: registers[`REG_L] <= tmp;
endcase
end
`INSN_LD_reg_imm16: begin
case (cycle)
- 0: cycle <= 1;
+ 0: begin /* */ end
1: begin
case (opcode[5:4])
`INSN_reg16_BC: registers[`REG_C] <= 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_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
+ 0: registers[`REG_SPH] <= tmp;
+ 1: registers[`REG_SPL] <= tmp;
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;
+ 0: {registers[`REG_SPH],registers[`REG_SPL]} <=
+ {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+ 1: {registers[`REG_SPH],registers[`REG_SPL]} <=
+ {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+ 2: begin /* type F */ end
+ 3: begin /* type F */ end
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
+ 0: {registers[`REG_SPH],registers[`REG_SPL]} <=
+ {registers[`REG_SPH],registers[`REG_SPL]} + 1;
1: begin
case (opcode[5:4])
`INSN_stack_AF: registers[`REG_F] <= 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_DE: registers[`REG_D] <= rdata;
`INSN_stack_HL: registers[`REG_H] <= rdata;
endcase
- cycle <= 0;
end
endcase
end
`INSN_LDH_AC: begin
case (cycle)
- 0: cycle <= 1;
- 1: begin
- cycle <= 0;
- if (opcode[4])
- registers[`REG_A] <= rdata;
- end
+ 0: begin /* Type F */ end
+ 1: if (opcode[4])
+ registers[`REG_A] <= rdata;
endcase
end
`INSN_LDx_AHL: begin
case (cycle)
- 0: cycle <= 1;
+ 0: begin /* Type F */ end
1: begin
- cycle <= 0;
if (opcode[3])
registers[`REG_A] <= rdata;
{registers[`REG_H],registers[`REG_L]} <=
`INSN_ALU8: begin
if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0)) begin
/* Sit on our asses. */
- cycle <= 1;
end else begin /* Actually do the computation! */
case (opcode[5:3])
`INSN_alu_ADD: begin
`INSN_NOP: begin /* NOP! */ end
`INSN_RST: begin
case (cycle)
- 0: cycle <= 1;
- 1: cycle <= 2;
- 2: cycle <= 3;
+ 0: begin /* type F */ end
+ 1: begin /* type F */ end
+ 2: begin /* type F */ end
+ 3: {registers[`REG_SPH],registers[`REG_SPL]} <=
+ {registers[`REG_SPH],registers[`REG_SPL]}-2;
+ endcase
+ end
+ `INSN_RET: begin
+ case (cycle)
+ 0: begin /* type F */ end
+ 1: registers[`REG_PCL] <= rdata;
+ 2: registers[`REG_PCH] <= rdata;
3: begin
- cycle <= 0;
{registers[`REG_SPH],registers[`REG_SPL]} <=
- {registers[`REG_SPH],registers[`REG_SPL]}-2;
+ {registers[`REG_SPH],registers[`REG_SPL]} + 2;
+ if (opcode[4]) /* RETI */
+ ie <= 1;
+ end
+ endcase
+ end
+ `INSN_CALL: begin
+ case (cycle)
+ 0: begin /* type F */ end
+ 1: tmp <= rdata; // tmp contains newpcl
+ 2: tmp2 <= rdata; // tmp2 contains newpch
+ 3: begin /* type F */ end
+ 4: registers[`REG_PCH] <= tmp2;
+ 5: begin
+ {registers[`REG_SPH],registers[`REG_SPL]} <=
+ {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+ registers[`REG_PCL] <= tmp;
end
endcase
end
+ default:
+ $stop;
endcase
state <= `STATE_FETCH;
end
endmodule
`timescale 1ns / 1ps
+module ROM(
+ input [15:0] address,
+ inout [7:0] data,
+ input clk,
+ input wr, rd);
+
+ reg [7:0] rom [2047:0];
+ initial $readmemh("rom.hex", rom);
+
+ wire decode = address[15:13] == 0;
+ wire [7:0] odata = rom[address[11:0]];
+ assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
+ //assign data = rd ? odata : 8'bzzzzzzzz;
+endmodule
+
+module InternalRAM(
+ input [15:0] address,
+ inout [7:0] data,
+ input clk,
+ input wr, rd);
+
+ reg [7:0] ram [8191:0];
+
+ wire decode = (address >= 16'hC000) && (address < 16'hFE00);
+ reg [7:0] odata;
+ wire idata = data;
+ assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
+
+ always @(negedge clk)
+ begin
+ if (decode && rd)
+ odata <= ram[address[12:0]];
+ else if (decode && wr)
+ ram[address[12:0]] <= data;
+ end
+endmodule
+
+module Switches(
+ input [15:0] address,
+ inout [7:0] data,
+ input clk,
+ input wr, rd,
+ input [7:0] switches,
+ output reg [7:0] ledout);
+
+ wire decode = address == 16'hFF51;
+ reg [7:0] odata;
+ wire idata = data;
+ assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
+
+ always @(negedge clk)
+ begin
+ if (decode && rd)
+ odata <= switches;
+ else if (decode && wr)
+ ledout <= data;
+ end
+endmodule
+
+module CoreTop(
+ input xtal,
+ input [1:0] switches,
+ output wire [7:0] leds,
+ output serio,
+ output wire [3:0] digits,
+ output wire [7:0] seven);
+
+ wire clk;
+ //IBUFG ibuf (.O(clk), .I(iclk));
+
+ CPUDCM dcm (.CLKIN_IN(xtal), .CLKFX_OUT(clk));
+
+ wire [15:0] addr;
+ wire [7:0] data;
+ wire wr, rd;
+
+ wire [7:0] ledout;
+ assign leds = switches[1] ? (switches[0]?{rd,wr,addr[5:0]}:data[7:0])
+ : ledout;
+
+ GBZ80Core core(
+ .clk(clk),
+ .busaddress(addr),
+ .busdata(data),
+ .buswr(wr),
+ .busrd(rd));
+
+ ROM rom(
+ .address(addr),
+ .data(data),
+ .clk(clk),
+ .wr(wr),
+ .rd(rd));
+
+ AddrMon amon(
+ .addr(addr),
+ .clk(clk),
+ .digit(digits),
+ .out(seven)
+ );
+
+ Switches sw(
+ .address(addr),
+ .data(data),
+ .clk(clk),
+ .wr(wr),
+ .rd(rd),
+ .ledout(ledout),
+ .switches(0)
+ );
+
+ UART nouart (
+ .clk(clk),
+ .wr(wr),
+ .rd(rd),
+ .addr(addr),
+ .data(data),
+ .serial(serio)
+ );
+endmodule
+
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);
+// wire [7:0] leds;
+// wire [7:0] switches;
+
always #10 clk <= ~clk;
GBZ80Core core(
.clk(clk),
.busdata(data),
.buswr(wr),
.busrd(rd));
- assign data = rd ? rom[addr] : 8'bzzzzzzzz;
+
+ ROM rom(
+ .clk(clk),
+ .address(addr),
+ .data(data),
+ .wr(wr),
+ .rd(rd));
+
+// InternalRAM ram(
+// .address(addr),
+// .data(data),
+// .clk(clk),
+// .wr(wr),
+// .rd(rd));
+
+// wire serio;
+// UART uart(
+// .addr(addr),
+// .data(data),
+// .clk(clk),
+// .wr(wr),
+// .rd(rd),
+// .serial(serio));
+
+// Switches sw(
+// .clk(clk),
+// .address(addr),
+// .data(data),
+// .wr(wr),
+// .rd(rd),
+// .switches(switches),
+// .leds(leds));
endmodule
git.joshuawise.com / fpgaboy.git / blobdiff