X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/7d9d69c71187b4891b2281ab58ab8360e43290c2..5f7913a508f18ca9664223dde5ae16608595a08b:/GBZ80Core.v diff --git a/GBZ80Core.v b/GBZ80Core.v index 3bc2b16..fef4de2 100644 --- a/GBZ80Core.v +++ b/GBZ80Core.v @@ -36,7 +36,24 @@ `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 @@ -62,15 +79,24 @@ `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 module GBZ80Core( input clk, - output reg [15:0] busaddress, /* BUS_* is latched on STATE_FETCH. */ + output reg [15:0] busaddress = 0, /* BUS_* is latched on STATE_FETCH. */ inout [7:0] busdata, - output reg buswr, output reg busrd); + output reg buswr = 0, output reg busrd = 0, + 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]; @@ -79,14 +105,14 @@ module GBZ80Core( 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, tmp2; /* Generic temporary regs. */ reg [7:0] buswdata; assign busdata = buswr ? buswdata : 8'bzzzzzzzz; - reg ie = 0; + reg ie = 0, iedelay = 0; initial begin registers[ 0] <= 0; @@ -101,12 +127,19 @@ module GBZ80Core( registers[ 9] <= 0; registers[10] <= 0; registers[11] <= 0; - ie <= 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) @@ -127,7 +160,10 @@ module GBZ80Core( 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; @@ -135,6 +171,10 @@ module GBZ80Core( if (rd) rdata <= busdata; cycle <= cycle + 1; end + if (iedelay) begin + ie <= 1; + iedelay <= 0; + end buswr <= 0; busrd <= 0; wr <= 0; @@ -265,7 +305,7 @@ module GBZ80Core( end 1: begin wr <= 1; - address <= {registers[`REG_SPH],registers[`REG_SPL]}-1; + address <= {registers[`REG_SPH],registers[`REG_SPL]}-2; case (opcode[5:4]) `INSN_stack_AF: wdata <= registers[`REG_F]; `INSN_stack_BC: wdata <= registers[`REG_C]; @@ -273,7 +313,7 @@ module GBZ80Core( `INSN_stack_HL: wdata <= registers[`REG_L]; endcase end - 2: begin /* TWIDDLE OUR FUCKING THUMBS! */ end + 2: begin /* Twiddle thumbs. */ end 3: begin `EXEC_NEWCYCLE; `EXEC_INC_PC; @@ -288,7 +328,7 @@ module GBZ80Core( end 1: begin rd <= 1; - address <= {registers[`REG_SPH],registers[`REG_SPL]}; + address <= {registers[`REG_SPH],registers[`REG_SPL]} + 1; end 2: begin `EXEC_NEWCYCLE; @@ -350,6 +390,10 @@ module GBZ80Core( endcase end end + `INSN_ALU_A: begin + `EXEC_NEWCYCLE; + `EXEC_INC_PC; + end `INSN_NOP: begin `EXEC_NEWCYCLE; `EXEC_INC_PC; @@ -376,24 +420,35 @@ module GBZ80Core( end endcase end - `INSN_RET: begin + `INSN_RET,`INSN_RETCC: begin case (cycle) 0: begin rd <= 1; address <= {registers[`REG_SPH],registers[`REG_SPL]}; end - 1: begin + 1: begin // SPECIAL CASE: cycle does NOT increase linearly with ret! + `EXEC_INC_PC; // cycle 1 is skipped if we are not retcc + case (opcode[4:3]) + `INSN_cc_NZ: if (registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_Z: if (~registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_NC: if (registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + `INSN_cc_C: if (~registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + endcase + rd <= 1; + address <= {registers[`REG_SPH],registers[`REG_SPL]}; + end + 2: begin rd <= 1; address <= {registers[`REG_SPH],registers[`REG_SPL]} + 1; end - 2: begin /* twiddle thumbs */ end - 3: begin + 3: begin /* twiddle thumbs */ end + 4: begin `EXEC_NEWCYCLE; // do NOT increment PC! end endcase end - `INSN_CALL: begin + `INSN_CALL,`INSN_CALLCC: begin case (cycle) 0: begin `EXEC_INC_PC; @@ -407,6 +462,14 @@ module GBZ80Core( end 2: begin `EXEC_INC_PC; + if (!opcode[0]) // i.e., is callcc + /* We need to check the condition code to bail out. */ + case (opcode[4:3]) + `INSN_cc_NZ: if (registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_Z: if (~registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_NC: if (registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + `INSN_cc_C: if (~registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + endcase end 3: begin address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1; @@ -423,6 +486,115 @@ module GBZ80Core( end endcase end + `INSN_JP_imm,`INSN_JPCC_imm: 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; + if (!opcode[0]) begin // i.e., JP cc,nn + /* We need to check the condition code to bail out. */ + case (opcode[4:3]) + `INSN_cc_NZ: if (registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_Z: if (~registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_NC: if (registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + `INSN_cc_C: if (~registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + endcase + end + end + 3: begin + `EXEC_NEWCYCLE; + end + endcase + end + `INSN_JP_HL: begin + `EXEC_NEWCYCLE; + end + `INSN_JR_imm,`INSN_JRCC_imm: begin + case (cycle) + 0: begin + `EXEC_INC_PC; + `EXEC_NEXTADDR_PCINC; + rd <= 1; + end + 1: begin + `EXEC_INC_PC; + if (opcode[5]) begin // i.e., JP cc,nn + /* We need to check the condition code to bail out. */ + case (opcode[4:3]) + `INSN_cc_NZ: if (registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_Z: if (~registers[`REG_F][7]) begin `EXEC_NEWCYCLE; end + `INSN_cc_NC: if (registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + `INSN_cc_C: if (~registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end + endcase + end + end + 2: begin + `EXEC_NEWCYCLE; + end + endcase + end + `INSN_INCDEC16: begin + case (cycle) + 0: begin + case (opcode[5:4]) + `INSN_reg16_BC: begin + tmp <= registers[`REG_B]; + tmp2 <= registers[`REG_C]; + end + `INSN_reg16_DE: begin + tmp <= registers[`REG_D]; + tmp2 <= registers[`REG_E]; + end + `INSN_reg16_HL: begin + tmp <= registers[`REG_H]; + tmp2 <= registers[`REG_L]; + end + `INSN_reg16_SP: begin + tmp <= registers[`REG_SPH]; + tmp2 <= registers[`REG_SPL]; + end + endcase + end + 1: begin + `EXEC_INC_PC; + `EXEC_NEWCYCLE; + end + endcase + end + `INSN_VOP_INTR: begin + case (cycle) + 0: begin + address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1; + wdata <= registers[`REG_PCH]; + wr <= 1; + end + 1: begin + address <= {registers[`REG_SPH],registers[`REG_SPL]} - 2; + wdata <= registers[`REG_PCL]; + wr <= 1; + end + 2: begin + `EXEC_NEWCYCLE; + end + endcase + end + `INSN_DI: begin + `EXEC_NEWCYCLE; + `EXEC_INC_PC; + end + `INSN_EI: begin + `EXEC_NEWCYCLE; + `EXEC_INC_PC; + end default: $stop; endcase @@ -508,18 +680,16 @@ module GBZ80Core( end `INSN_PUSH_reg: begin /* PUSH is 16 cycles! */ case (cycle) - 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; + 0: begin /* type F */ end + 1: begin /* type F */ end 2: begin /* type F */ end - 3: begin /* type F */ end + 3: {registers[`REG_SPH],registers[`REG_SPL]} <= + {registers[`REG_SPH],registers[`REG_SPL]} - 2; endcase end `INSN_POP_reg: begin /* POP is 12 cycles! */ case (cycle) - 0: {registers[`REG_SPH],registers[`REG_SPL]} <= - {registers[`REG_SPH],registers[`REG_SPL]} + 1; + 0: begin end 1: begin case (opcode[5:4]) `INSN_stack_AF: registers[`REG_F] <= rdata; @@ -527,8 +697,6 @@ module GBZ80Core( `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; end 2: begin case (opcode[5:4]) @@ -537,6 +705,8 @@ module GBZ80Core( `INSN_stack_DE: registers[`REG_D] <= rdata; `INSN_stack_HL: registers[`REG_H] <= rdata; endcase + {registers[`REG_SPH],registers[`REG_SPL]} <= + {registers[`REG_SPH],registers[`REG_SPL]} + 2; end endcase end @@ -587,6 +757,28 @@ module GBZ80Core( registers[`REG_F][3:0] }; end + `INSN_alu_SUB: begin + registers[`REG_A] <= + registers[`REG_A] - tmp; + registers[`REG_F] <= + { /* Z */ ((registers[`REG_A] - tmp) == 0) ? 1'b1 : 1'b0, + /* N */ 1'b1, + /* H */ (({1'b0,registers[`REG_A][3:0]} - {1'b0,tmp[3:0]}) >> 4 == 1) ? 1'b1 : 1'b0, + /* C */ (({1'b0,registers[`REG_A]} - {1'b0,tmp}) >> 8 == 1) ? 1'b1 : 1'b0, + registers[`REG_F][3:0] + }; + end + `INSN_alu_SBC: begin + registers[`REG_A] <= + registers[`REG_A] - (tmp + {7'b0,registers[`REG_F][4]}); + registers[`REG_F] <= + { /* Z */ ((registers[`REG_A] - (tmp + {7'b0,registers[`REG_F][4]})) == 0) ? 1'b1 : 1'b0, + /* N */ 1'b1, + /* H */ (({1'b0,registers[`REG_A][3:0]} - ({1'b0,tmp[3:0]} + {4'b0,registers[`REG_F][4]})) >> 4 == 1) ? 1'b1 : 1'b0, + /* C */ (({1'b0,registers[`REG_A]} - ({1'b0,tmp} + {8'b0,registers[`REG_F][4]})) >> 8 == 1) ? 1'b1 : 1'b0, + registers[`REG_F][3:0] + }; + end `INSN_alu_AND: begin registers[`REG_A] <= registers[`REG_A] & tmp; @@ -614,11 +806,50 @@ module GBZ80Core( registers[`REG_F][3:0] }; end + `INSN_alu_CP: begin + registers[`REG_F] <= + { /* Z */ ((registers[`REG_A] - tmp) == 0) ? 1'b1 : 1'b0, + /* N */ 1'b1, + /* H */ (({1'b0,registers[`REG_A][3:0]} - {1'b0,tmp[3:0]}) >> 4 == 1) ? 1'b1 : 1'b0, + /* C */ (({1'b0,registers[`REG_A]} - {1'b0,tmp}) >> 8 == 1) ? 1'b1 : 1'b0, + registers[`REG_F][3:0] + }; + end default: $stop; endcase end end + `INSN_ALU_A: begin + case(opcode[5:3]) + `INSN_alu_RLCA: begin + registers[`REG_A] <= {registers[`REG_A][6:0],registers[`REG_A][7]}; + registers[`REG_F] <= {registers[`REG_F][7:5],registers[`REG_A][7],registers[`REG_F][3:0]}; + end + `INSN_alu_RRCA: begin + registers[`REG_A] <= {registers[`REG_A][0],registers[`REG_A][7:1]}; + registers[`REG_F] <= {registers[`REG_F][7:5],registers[`REG_A][0],registers[`REG_F][3:0]}; + end + `INSN_alu_RLA: begin + registers[`REG_A] <= {registers[`REG_A][6:0],registers[`REG_F][4]}; + registers[`REG_F] <= {registers[`REG_F][7:5],registers[`REG_A][7],registers[`REG_F][3:0]}; + end + `INSN_alu_RRA: begin + registers[`REG_A] <= {registers[`REG_A][4],registers[`REG_A][7:1]}; + registers[`REG_F] <= {registers[`REG_F][7:5],registers[`REG_A][0],registers[`REG_F][3:0]}; + end + `INSN_alu_CPL: begin + registers[`REG_A] <= ~registers[`REG_A]; + registers[`REG_F] <= {registers[`REG_F][7],1'b1,1'b1,registers[`REG_F][4:0]}; + end + `INSN_alu_SCF: begin + registers[`REG_F] <= {registers[`REG_F][7:5],1'b1,registers[`REG_F][3:0]}; + end + `INSN_alu_CCF: begin + registers[`REG_F] <= {registers[`REG_F][7:5],~registers[`REG_F][4],registers[`REG_F][3:0]}; + end + endcase + end `INSN_NOP: begin /* NOP! */ end `INSN_RST: begin case (cycle) @@ -629,20 +860,22 @@ module GBZ80Core( {registers[`REG_SPH],registers[`REG_SPL]}-2; endcase end - `INSN_RET: begin + `INSN_RET,`INSN_RETCC: begin case (cycle) - 0: begin /* type F */ end - 1: registers[`REG_PCL] <= rdata; - 2: registers[`REG_PCH] <= rdata; - 3: begin + 0: if (opcode[0]) // i.e., not RETCC + cycle <= 1; // Skip cycle 1; it gets incremented on the next round. + 1: begin /* Nothing need happen here. */ end + 2: registers[`REG_PCL] <= rdata; + 3: registers[`REG_PCH] <= rdata; + 4: begin {registers[`REG_SPH],registers[`REG_SPL]} <= {registers[`REG_SPH],registers[`REG_SPL]} + 2; - if (opcode[4]) /* RETI */ + if (opcode[4] && opcode[0]) /* RETI */ ie <= 1; end endcase end - `INSN_CALL: begin + `INSN_CALL,`INSN_CALLCC: begin case (cycle) 0: begin /* type F */ end 1: tmp <= rdata; // tmp contains newpcl @@ -656,6 +889,69 @@ module GBZ80Core( end endcase end + `INSN_JP_imm,`INSN_JPCC_imm: begin + case (cycle) + 0: begin /* type F */ end + 1: tmp <= rdata; // tmp contains newpcl + 2: tmp2 <= rdata; // tmp2 contains newpch + 3: {registers[`REG_PCH],registers[`REG_PCL]} <= + {tmp2,tmp}; + endcase + end + `INSN_JP_HL: begin + {registers[`REG_PCH],registers[`REG_PCL]} <= + {registers[`REG_H],registers[`REG_L]}; + end + `INSN_JR_imm,`INSN_JRCC_imm: begin + case (cycle) + 0: begin /* type F */ end + 1: tmp <= rdata; + 2: {registers[`REG_PCH],registers[`REG_PCL]} <= + {registers[`REG_PCH],registers[`REG_PCL]} + + {tmp[7]?8'hFF:8'h00,tmp}; + endcase + end + `INSN_INCDEC16: begin + case (cycle) + 0: {tmp,tmp2} <= {tmp,tmp2} + + (opcode[3] ? 16'hFFFF : 16'h0001); + 1: begin + case (opcode[5:4]) + `INSN_reg16_BC: begin + registers[`REG_B] <= tmp; + registers[`REG_C] <= tmp2; + end + `INSN_reg16_DE: begin + registers[`REG_D] <= tmp; + registers[`REG_E] <= tmp2; + end + `INSN_reg16_HL: begin + registers[`REG_H] <= tmp; + registers[`REG_L] <= tmp2; + end + `INSN_reg16_SP: begin + registers[`REG_SPH] <= tmp; + registers[`REG_SPL] <= tmp2; + end + endcase + end + endcase + end + `INSN_VOP_INTR: begin + case (cycle) + 0: begin end + 1: begin end + 2: begin + ie <= 0; + {registers[`REG_PCH],registers[`REG_PCL]} <= + {8'b0,jaddr}; + {registers[`REG_SPH],registers[`REG_SPL]} <= + {registers[`REG_SPH],registers[`REG_SPL]} - 2; + end + endcase + end + `INSN_DI: ie <= 0; + `INSN_EI: iedelay <= 1; default: $stop; endcase @@ -663,175 +959,3 @@ module GBZ80Core( end endcase 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; - -// wire [7:0] leds; -// wire [7:0] switches; - - always #10 clk <= ~clk; - GBZ80Core core( - .clk(clk), - .busaddress(addr), - .busdata(data), - .buswr(wr), - .busrd(rd)); - - 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