X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/722e486a9ea69af1fdad7d0d31490bb2845881ec..3ad960bdb71efcbb1dfd436163085da0d70eb699:/GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 77c3649..f41805a 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -36,6 +36,7 @@
 `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
@@ -44,6 +45,10 @@
 `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
@@ -87,10 +92,11 @@ module GBZ80Core(
 	input clk,
 	output reg [15:0] busaddress,	/* BUS_* is latched on STATE_FETCH. */
 	inout [7:0] busdata,
-	output reg buswr, output reg busrd);
+	output reg buswr, output reg busrd,
+	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];
 	
@@ -99,14 +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, iedelay;
 	
 	initial begin
 		registers[ 0] <= 0;
@@ -121,12 +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)
@@ -147,7 +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;
@@ -155,6 +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;
@@ -171,213 +191,9 @@ module GBZ80Core(
 `define EXEC_NEWCYCLE \
 	newcycle <= 1; rd <= 1; wr <= 0
 			casex (opcode)
-			`INSN_LD_reg_imm8: begin
-				case (cycle)
-				0:	begin
-						`EXEC_INC_PC;
-						`EXEC_NEXTADDR_PCINC;
-						rd <= 1;
-					end
-				1:	begin
-						`EXEC_INC_PC;
-						if (opcode[5:3] == `INSN_reg_dHL) begin
-							address <= {registers[`REG_H], registers[`REG_L]};
-							wdata <= rdata;
-							rd <= 0;
-							wr <= 1;
-						end else begin
-							`EXEC_NEWCYCLE;
-						end
-					end
-				2:	begin
-						`EXEC_NEWCYCLE;
-					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:	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
-				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:	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
+			`define EXECUTE
+			`include "allinsns.v"
+			`undef EXECUTE
 			`INSN_RST: begin
 				case (cycle)
 				0:	begin
@@ -400,18 +216,29 @@ 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
@@ -511,264 +338,69 @@ module GBZ80Core(
 					end
 				endcase
 			end
-			default:
-				$stop;
-			endcase
-			state <= `STATE_WRITEBACK;
-		end
-		`STATE_WRITEBACK: begin
-			casex (opcode)
-			`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
+			`INSN_INCDEC16: begin
 				case (cycle)
-				0:	begin /* */ end
-				1:	begin
+				0: 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;
+						`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
-				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
+				1: begin
+						`EXEC_INC_PC;
+						`EXEC_NEWCYCLE;
 					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! */
+			`INSN_VOP_INTR: begin
 				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;
+				0:	begin
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+						wdata <= registers[`REG_PCH];
+						wr <= 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;
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+						wdata <= registers[`REG_PCL];
+						wr <= 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
-					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);
+						`EXEC_NEWCYCLE;
 					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
-				end
+			`INSN_DI: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
 			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,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
+			`INSN_EI: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
 			end
-			`INSN_NOP: begin /* NOP! */ end
+			default:
+				$stop;
+			endcase
+			state <= `STATE_WRITEBACK;
+		end
+		`STATE_WRITEBACK: begin
+			casex (opcode)
+			`define WRITEBACK
+			`include "allinsns.v"
+			`undef WRITEBACK
 			`INSN_RST: begin
 				case (cycle)
 				0:	begin /* type F */ end
@@ -778,15 +410,17 @@ 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
@@ -827,6 +461,47 @@ module GBZ80Core(
 						{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