X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/fa136d635a2e9dea677566536f71e69489dbb200..ef6fbe3130c958177759bd99cf24a6c3edc4693c:/GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index b7994ae..cb231c2 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -32,6 +32,11 @@
 `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_CALL				8'b11001101
 
 `define INSN_reg_A		3'b111
 `define INSN_reg_B		3'b000
@@ -49,6 +54,15 @@
 `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?
+
 module GBZ80Core(
 	input clk,
 	output reg [15:0] busaddress,	/* BUS_* is latched on STATE_FETCH. */
@@ -67,11 +81,13 @@ module GBZ80Core(
 	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;
@@ -131,7 +147,7 @@ module GBZ80Core(
 						`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]};
@@ -142,7 +158,7 @@ module GBZ80Core(
 							`EXEC_NEWCYCLE;
 						end
 					end
-				2: begin
+				2:	begin
 						`EXEC_NEWCYCLE;
 					end
 				endcase
@@ -155,13 +171,13 @@ module GBZ80Core(
 				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;
@@ -174,11 +190,11 @@ module GBZ80Core(
 			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;
@@ -189,13 +205,13 @@ module GBZ80Core(
 				`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
@@ -226,7 +242,7 @@ module GBZ80Core(
 			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])
@@ -236,7 +252,7 @@ module GBZ80Core(
 						`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])
@@ -247,7 +263,7 @@ module GBZ80Core(
 						endcase
 					end
 				2:	begin /* TWIDDLE OUR FUCKING THUMBS! */ end
-				3: begin
+				3:	begin
 						`EXEC_NEWCYCLE;
 						`EXEC_INC_PC;
 					end
@@ -255,15 +271,15 @@ module GBZ80Core(
 			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
@@ -280,7 +296,7 @@ module GBZ80Core(
 							wdata <= registers[`REG_A];
 						end
 					end
-				1: begin
+				1:	begin
 						`EXEC_NEWCYCLE;
 						`EXEC_INC_PC;
 					end
@@ -288,7 +304,7 @@ module GBZ80Core(
 			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;
@@ -303,6 +319,97 @@ module GBZ80Core(
 					end
 				endcase
 			end
+			`INSN_ALU8: begin
+				if ((opcode[2:0] == `INSN_reg_dHL) && (cycle == 0)) begin
+					// fffffffff fuck your shit, read from (HL) :(
+					rd <= 1;
+					address <= {registers[`REG_H], registers[`REG_L]};
+				end else begin
+					`EXEC_NEWCYCLE;
+					`EXEC_INC_PC;
+					case (opcode[2:0])
+					`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
+			`INSN_NOP: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
+			end
+			`INSN_RST: begin
+				case (cycle)
+				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
+				2:	begin
+						wr <= 1;
+						address <= {registers[`REG_SPH],registers[`REG_SPL]}-2;
+						wdata <= registers[`REG_PCL];
+					end
+				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
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+						wdata <= registers[`REG_PCH];
+						wr <= 1;
+					end
+				3:	begin
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+						wdata <= registers[`REG_PCL];
+						wr <= 1;
+					end
+				4:	begin /* nothing happens on the bus next cycle! */ end
+				5:	begin
+						`EXEC_NEWCYCLE;	/* do NOT increment the PC */
+					end
+				endcase
+			end
 			default:
 				$stop;
 			endcase
@@ -312,8 +419,8 @@ module GBZ80Core(
 			casex (opcode)
 			`INSN_LD_reg_imm8:
 				case (cycle)
-				0: cycle <= 1;
-				1: case (opcode[5:3])
+				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
@@ -323,7 +430,7 @@ module GBZ80Core(
 					`INSN_reg_L:	begin registers[`REG_L] <= rdata; cycle <= 0; end
 					`INSN_reg_dHL:	cycle <= 2;
 					endcase
-				2: cycle <= 0;
+				2:	cycle <= 0;
 				endcase
 			`INSN_HALT: begin
 				/* Nothing needs happen here. */
@@ -331,8 +438,8 @@ module GBZ80Core(
 			end
 			`INSN_LD_HL_reg: begin
 				case (cycle)
-				0: cycle <= 1;
-				1: cycle <= 0;
+				0:	cycle <= 1;
+				1:	cycle <= 0;
 				endcase
 			end
 			`INSN_LD_reg_HL: begin
@@ -340,13 +447,13 @@ module GBZ80Core(
 				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
+						`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
@@ -354,13 +461,13 @@ module GBZ80Core(
 			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
@@ -467,6 +574,127 @@ module GBZ80Core(
 					end
 				endcase
 			end
+			`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
+						registers[`REG_A] <=
+							registers[`REG_A] + tmp;
+						registers[`REG_F] <=
+							{ /* Z */ ((registers[`REG_A] + tmp) == 0) ? 1'b1 : 1'b0,
+							  /* N */ 1'b0,
+							  /* 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_ADC: 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'b0,
+							  /* 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;
+						registers[`REG_F] <=
+							{ /* Z */ ((registers[`REG_A] & tmp) == 0) ? 1'b1 : 1'b0,
+							  3'b010,
+							  registers[`REG_F][3:0]
+							};
+					end
+					`INSN_alu_OR: begin
+						registers[`REG_A] <=
+							registers[`REG_A] | tmp;
+						registers[`REG_F] <=
+							{ /* Z */ ((registers[`REG_A] | tmp) == 0) ? 1'b1 : 1'b0,
+							  3'b000,
+							  registers[`REG_F][3:0]
+							};
+					end
+					`INSN_alu_XOR: begin
+						registers[`REG_A] <=
+							registers[`REG_A] ^ tmp;
+						registers[`REG_F] <=
+							{ /* Z */ ((registers[`REG_A] ^ tmp) == 0) ? 1'b1 : 1'b0,
+							  3'b000,
+							  registers[`REG_F][3:0]
+							};
+					end
+					default:
+						$stop;
+					endcase
+				end
+			end
+			`INSN_NOP: begin /* NOP! */ end
+			`INSN_RST: begin
+				case (cycle)
+				0:	cycle <= 1;
+				1:	cycle <= 2;
+				2:	cycle <= 3;
+				3:	begin
+						cycle <= 0;
+						{registers[`REG_SPH],registers[`REG_SPL]} <=
+							{registers[`REG_SPH],registers[`REG_SPL]}-2;
+					end
+				endcase
+			end
+			`INSN_RET: begin
+				case (cycle)
+				0:	cycle <= 1;
+				1:	begin
+						cycle <= 2;
+						registers[`REG_PCL] <= rdata;
+					end
+				2:	begin
+						cycle <= 3;
+						registers[`REG_PCH] <= rdata;
+					end
+				3:	begin
+						cycle <= 0;
+						{registers[`REG_SPH],registers[`REG_SPL]} <=
+							{registers[`REG_SPH],registers[`REG_SPL]} + 2;
+						if (opcode[4])	/* RETI */
+							ie <= 1;
+					end
+				endcase
+			end
+			`INSN_CALL: begin
+				case (cycle)
+				0:	cycle <= 1;
+				1:	begin
+						cycle <= 2;
+						tmp <= rdata;	// tmp contains newpcl
+					end
+				2:	begin
+						cycle <= 3;
+						tmp2 <= rdata;	// tmp2 contains newpch
+					end
+				3: begin
+						cycle <= 4;
+						registers[`REG_PCH] <= tmp2;
+					end
+				4: begin
+						cycle <= 5;
+						registers[`REG_PCL] <= tmp;
+					end
+				5: begin
+						{registers[`REG_SPH],registers[`REG_SPL]} <=
+							{registers[`REG_SPH],registers[`REG_SPL]} - 2;
+						cycle <= 0;
+					end
+				endcase
+			end
+			default:
+				$stop;
 			endcase
 			state <= `STATE_FETCH;
 		end
@@ -474,14 +702,53 @@ module GBZ80Core(
 endmodule
 
 `timescale 1ns / 1ps
+module ROM(
+	input [15:0] address,
+	inout [7:0] data,
+	input wr, rd);
+
+	reg [7:0] rom [2047:0];
+	initial $readmemh("rom.hex", rom);
+
+	wire decode = address[15:13] == 0;
+	reg [7:0] odata;
+	wire idata = data;
+	assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
+	
+	always @(wr or rd)
+	begin
+		if (decode && rd)
+			odata <= rom[address];
+	end
+endmodule
+
+module InternalRAM(
+	input [15:0] address,
+	inout [7:0] data,
+	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 @(rd or wr)
+	begin
+		if (decode && rd)
+			odata <= ram[address];
+		else if (decode && wr)
+			ram[address] <= idata;
+	end
+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);
 	always #10 clk <= ~clk;
 	GBZ80Core core(
 		.clk(clk),
@@ -489,5 +756,16 @@ module TestBench();
 		.busdata(data),
 		.buswr(wr),
 		.busrd(rd));
-	assign data = rd ? rom[addr] : 8'bzzzzzzzz;
+	
+	ROM rom(
+		.address(addr),
+		.data(data),
+		.wr(wr),
+		.rd(rd));
+	
+	InternalRAM ram(
+		.address(addr),
+		.data(data),
+		.wr(wr),
+		.rd(rd));
 endmodule