X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/2f55f80959676970f85a02a9a968668ae2113dda..6dbce0b54fbfff7fee918b9033c0111065ce582a:/GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 9bc60a8..1aaa01c 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -22,14 +22,42 @@
 `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_LD_reg_imm16	8'b00xx0001
+`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_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
+`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?
 
 module GBZ80Core(
 	input clk,
@@ -49,22 +77,24 @@ 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] buswdata;
 	assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
 	
 	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;
 	end
 
 	always @(posedge clk)
@@ -84,11 +114,16 @@ module GBZ80Core(
 			if (newcycle) begin
 				opcode <= busdata;
 				rdata <= busdata;
+				newcycle <= 0;
 				cycle <= 0;
 			end else
 				if (rd) rdata <= busdata;
 			buswr <= 0;
 			busrd <= 0;
+			wr <= 0;
+			rd <= 0;
+			address <= 16'bxxxxxxxxxxxxxxxx;	// Make it obvious if something of type has happened.
+			wdata <= 8'bxxxxxxxx;
 			state <= `STATE_EXECUTE;
 		end
 		`STATE_EXECUTE: begin
@@ -104,12 +139,11 @@ module GBZ80Core(
 				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;
@@ -123,26 +157,406 @@ module GBZ80Core(
 					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
+			`INSN_LDH_AC: begin
+				case (cycle)
+				0:	begin
+						address <= {8'hFF,registers[`REG_C]};
+						if (opcode[4]) begin	// LD A,(C)
+							rd <= 1;
+						end else begin
+							wr <= 1;
+							wdata <= registers[`REG_A];
+						end
+					end
+				1: begin
+						`EXEC_NEWCYCLE;
+						`EXEC_INC_PC;
+					end
+				endcase
+			end
+			`INSN_LDx_AHL: begin
+				case (cycle)
+				0: begin
+						address <= {registers[`REG_H],registers[`REG_L]};
+						if (opcode[3]) begin	// LDx A, (HL)
+							rd <= 1;
+						end else begin
+							wr <= 1;
+							wdata <= registers[`REG_A];
+						end
+					end
+				1:	begin
+						`EXEC_NEWCYCLE;
+						`EXEC_INC_PC;
+					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:	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
+					endcase
+				end
+			end
+			default:
+				$stop;
 			endcase
 			state <= `STATE_WRITEBACK;
 		end
 		`STATE_WRITEBACK: begin
 			casex (opcode)
-				`INSN_LD_reg_imm8:
-					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_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
-					2: cycle <= 0;
+						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
+			`INSN_LDH_AC: begin
+				case (cycle)
+				0:	cycle <= 1;
+				1: begin
+						cycle <= 0;
+						if (opcode[4])
+							registers[`REG_A] <= rdata;
+					end
+				endcase
+			end
+			`INSN_LDx_AHL: begin
+				case (cycle)
+				0:	cycle <= 1;
+				1:	begin
+						cycle <= 0;
+						if (opcode[3])
+							registers[`REG_A] <= rdata;
+						{registers[`REG_H],registers[`REG_L]} <=
+							opcode[4] ? // if set, LDD, else LDI
+							({registers[`REG_H],registers[`REG_L]} - 1) :
+							({registers[`REG_H],registers[`REG_L]} + 1);
+					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 */ 0,
+							  /* 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 */ 0,
+							  /* 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,
+							  0,1,0,
+							  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,
+							  0,0,0,
+							  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,
+							  0,0,0,
+							  registers[`REG_F][3:0]
+							};
+					end
+					default:
+						$stop;
 					endcase
+				end
+			end
 			endcase
 			state <= `STATE_FETCH;
 		end