X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/b85870e0cf3c61677a430559c9621a665a8bab6d..06ad3a30038ac8ca45dd7b0c34213c0c8335c17c:/GBZ80Core.v?ds=inline

diff --git a/GBZ80Core.v b/GBZ80Core.v
index e5a7d35..96e4dcd 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -26,6 +26,32 @@
 `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_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_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
 `define INSN_reg_C		3'b001
@@ -34,6 +60,30 @@
 `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?
+`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,
@@ -53,37 +103,48 @@ 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;
-		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;
+		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
@@ -92,10 +153,16 @@ module GBZ80Core(
 				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;
+			rd <= 0;
+			address <= 16'bxxxxxxxxxxxxxxxx;	// Make it obvious if something of type has happened.
+			wdata <= 8'bxxxxxxxx;
 			state <= `STATE_EXECUTE;
 		end
 		`STATE_EXECUTE: begin
@@ -113,7 +180,7 @@ 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]};
@@ -124,94 +191,715 @@ module GBZ80Core(
 							`EXEC_NEWCYCLE;
 						end
 					end
-				2: begin
+				2:	begin
 						`EXEC_NEWCYCLE;
 					end
 				endcase
 			end
 			`INSN_HALT: begin
-				/* XXX UNIMP */
+				`EXEC_NEWCYCLE;
+				/* XXX Interrupts needed for HALT. */
 			end
 			`INSN_LD_HL_reg: begin
-				/* XXX UNIMP */
+				case (cycle)
+				0:	begin
+						case (opcode[2:0])
+						`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
+				1:	begin
+						`EXEC_INC_PC;
+						`EXEC_NEWCYCLE;
+					end
+				endcase
 			end
 			`INSN_LD_reg_HL: begin
-				/* XXX UNIMP */
+				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
+				`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
+				`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 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:	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_ALU_A: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
+			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,`INSN_RETCC: begin
+				case (cycle)
+				0:	begin
+						rd <= 1;
+						address <= {registers[`REG_SPH],registers[`REG_SPL]};
+					end
+				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
+				3:	begin /* twiddle thumbs */ end
+				4:	begin
+						`EXEC_NEWCYCLE;
+						// do NOT increment PC!
+					end
+				endcase
+			end
+			`INSN_CALL,`INSN_CALLCC: 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])	// 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;
+						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
+			`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
+			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_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;
+			`INSN_LD_reg_imm8:
+				case (cycle)
+				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:	begin end
+				endcase
+			`INSN_HALT: begin
+				/* Nothing needs happen here. */
+				/* XXX Interrupts needed for HALT. */
+			end
+			`INSN_LD_HL_reg: begin
+				/* Nothing of interest here */
+			end
+			`INSN_LD_reg_HL: begin
+				case (cycle)
+				0:	begin end
+				1:	begin
+						case (opcode[5:3])
+						`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
+				endcase
+			end
+			`INSN_LD_reg_reg: begin
+				case (opcode[5:3])
+				`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:	begin /* */ end
+				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
+					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
+					end
+				endcase
+			end
+			`INSN_LD_SP_HL: begin
+				case (cycle)
+				0:	registers[`REG_SPH] <= tmp;
+				1: registers[`REG_SPL] <= tmp;
+				endcase
+			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;
+				2:	begin /* type F */ end
+				3:	begin /* type F */ end
+				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;
+				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;
+					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
-					2: cycle <= 0;
+					end
+				endcase
+			end
+			`INSN_LDH_AC: begin
+				case (cycle)
+				0:	begin /* Type F */ end
+				1:	if (opcode[4])
+						registers[`REG_A] <= rdata;
+				endcase
+			end
+			`INSN_LDx_AHL: begin
+				case (cycle)
+				0:	begin /* Type F */ end
+				1:	begin
+						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. */
+				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_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;
+						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
+					`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
-				`INSN_HALT: begin
-					/* XXX UNIMP */
 				end
-				`INSN_LD_HL_reg: begin
-					/* XXX UNIMP */
+			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_LD_reg_HL: begin
-					/* XXX UNIMP */
+				`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_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
+				`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,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)
+				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,`INSN_RETCC: begin
+				case (cycle)
+				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] && opcode[0])	/* RETI */
+							ie <= 1;
+					end
+				endcase
+			end
+			`INSN_CALL,`INSN_CALLCC: 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
+			`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
+			default:
+				$stop;
 			endcase
 			state <= `STATE_FETCH;
 		end
 		endcase
 endmodule
-
-`timescale 1ns / 1ps
-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),
-		.busaddress(addr),
-		.busdata(data),
-		.buswr(wr),
-		.busrd(rd));
-	assign data = rd ? rom[addr] : 8'bzzzzzzzz;
-endmodule