[fpgaboy.git] / GBZ80Core.v

`define REG_A	0
`define REG_B	1
`define REG_C	2
`define REG_D	3
`define REG_E	4
`define REG_F	5
`define REG_H	6
`define REG_L	7
`define REG_SPH	8
`define REG_SPL	9
`define REG_PCH	10
`define REG_PCL	11

`define _A	registers[`REG_A]
`define _B	registers[`REG_B]
`define _C	registers[`REG_C]
`define _D	registers[`REG_D]
`define _E	registers[`REG_E]
`define _F	registers[`REG_F]
`define _H	registers[`REG_H]
`define _L	registers[`REG_L]
`define _SPH	registers[`REG_SPH]
`define _SPL	registers[`REG_SPL]
`define _PCH	registers[`REG_PCH]
`define _PCL	registers[`REG_PCL]
`define _AF	{`_A, `_F}
`define _BC	{`_B, `_C}
`define _DE	{`_D, `_E}
`define _HL	{`_H, `_L}
`define _SP	{`_SPH, `_SPL}
`define _PC	{`_PCH, `_PCL}

`define FLAG_Z	8'b10000000
`define FLAG_N	8'b01000000
`define FLAG_H	8'b00100000
`define FLAG_C	8'b00010000

`define STATE_FETCH		2'h0
`define STATE_DECODE		2'h1
`define STATE_EXECUTE		2'h2
`define STATE_WRITEBACK		2'h3

`define INSN_LD_reg_imm8	9'b000xxx110
`define INSN_HALT		9'b001110110
`define INSN_LD_HL_reg		9'b001110xxx
`define INSN_LD_reg_HL		9'b001xxx110
`define INSN_LD_reg_reg		9'b001xxxxxx
`define INSN_LD_reg_imm16	9'b000xx0001
`define INSN_LD_SP_HL		9'b011111001
`define INSN_PUSH_reg		9'b011xx0101
`define INSN_POP_reg		9'b011xx0001
`define INSN_LDH_AC		9'b0111x0010	// Either LDH A,(C) or LDH (C),A
`define INSN_LDx_AHL		9'b0001xx010	// LDD/LDI A,(HL) / (HL),A
`define INSN_ALU8		9'b010xxxxxx	// 10 xxx yyy
`define INSN_ALU8IMM		9'b011xxx110
`define INSN_NOP		9'b000000000
`define INSN_RST		9'b011xxx111
`define INSN_RET		9'b0110x1001	// 1 = RETI, 0 = RET
`define INSN_RETCC		9'b0110xx000
`define INSN_CALL		9'b011001101
`define INSN_CALLCC		9'b0110xx100	// Not that call/cc.
`define INSN_JP_imm		9'b011000011
`define INSN_JPCC_imm		9'b0110xx010
`define INSN_ALU_A		9'b000xxx111
`define INSN_JP_HL		9'b011101001
`define INSN_JR_imm		9'b000011000
`define INSN_JRCC_imm		9'b0001xx000
`define INSN_INCDEC16		9'b000xxx011
`define INSN_VOP_INTR		9'b011111100	// 0xFC is grabbed by the fetch if there is an interrupt pending.
`define INSN_DI			9'b011110011
`define INSN_EI			9'b011111011
`define INSN_INCDEC_HL		9'b00011010x
`define INSN_INCDEC_reg8	9'b000xxx10x
`define INSN_LD8M_A		9'b0111x0000	// 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
`define INSN_LD16M_A		9'b0111x1010	// 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
`define INSN_LDBCDE_A		9'b0000xx010
`define INSN_TWO_BYTE		9'b011001011    // prefix for two-byte opqodes
`define INSN_ALU_EXT		9'b100xxxxxx
`define INSN_BIT		9'b101xxxxxx
`define INSN_RES		9'b110xxxxxx
`define INSN_SET		9'b111xxxxxx
`define INSN_ADD_HL		9'b000xx1001

`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
`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?
`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
`define INSN_alu_RLC		3'b000
`define INSN_alu_RRC		3'b001
`define INSN_alu_RL		3'b010
`define INSN_alu_RR		3'b011
`define INSN_alu_DA_SLA		3'b100
`define INSN_alu_CPL_SRA	3'b101
`define INSN_alu_SCF_SWAP	3'b110
`define INSN_alu_CCF_SRL	3'b111

`define EXEC_INC_PC 		`_PC <= `_PC + 1;
`define EXEC_NEXTADDR_PCINC	address <= `_PC + 1;
`define EXEC_NEWCYCLE		begin newcycle <= 1; rd <= 1; wr <= 0; end
`define EXEC_NEWCYCLE_TWOBYTE	begin newcycle <= 1; rd <= 1; wr <= 0; twobyte <= 1; end
`ifdef verilator
	`define EXEC_WRITE(ad, da)	begin address <= (ad); wdata <= (da); wr <= 1; end
	`define EXEC_READ(ad)		begin address <= (ad); rd <= 1; end
`else
	`ifdef isim
		`define EXEC_WRITE(ad, da)	begin address <= (ad); wdata <= (da); wr <= 1; end
		`define EXEC_READ(ad)		begin address <= (ad); rd <= 1; end
	`else
/* Work around XST's retarded bugs :\ */
		`define EXEC_WRITE(ad, da)	begin address <= (ad); wdata <= (da); wr <= 1; end end
		`define EXEC_READ(ad)		begin address <= (ad); rd <= 1; end end
	`endif
`endif

module GBZ80Core(
	input clk,
	inout [15:0] bus0address,	/* BUS_* is latched on STATE_FETCH. */
	inout [7:0] bus0data,
	inout bus0wr, bus0rd,
	inout [15:0] bus1address,	/* BUS_* is latched on STATE_FETCH. */
	inout [7:0] bus1data,
	inout bus1wr, bus1rd,
	input irq, output reg irqack, input [7:0] jaddr,
	output reg [1:0] state);

//	reg [1:0] state;					/* State within this bus cycle (see STATE_*). */
	reg [2:0] cycle;					/* Cycle for instructions. */
	
	reg [7:0] registers[11:0];
	
	reg [15:0] address;				/* Address for the next bus operation. */
	
	reg [8:0] 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, wr, newcycle, twobyte;
	
	reg [7:0] tmp, tmp2;			/* Generic temporary regs. */
	
	reg [7:0] buswdata;
	wire [7:0] busdata;
	
	reg [15:0] busaddress;
	reg buswr, busrd;
	
	reg bootstrap_enb;
	
	wire bus = ((busaddress[15:8] == 8'h00) && bootstrap_enb) || ((busaddress[15:7] == 9'b111111111) && (busaddress != 16'hFFFF))	/* 0 or 1 depending on which bus */
		`ifdef isim
			|| (busaddress === 16'hxxxx) /* To avoid simulator glomulation. */
		`endif
			;
		
	assign bus0address = (bus == 0) ? busaddress : 16'bzzzzzzzzzzzzzzz;
	assign bus1address = (bus == 1) ? busaddress : 16'bzzzzzzzzzzzzzzz;
	assign bus0data = ((bus == 0) && buswr) ? buswdata : 8'bzzzzzzzz;
	assign bus1data = ((bus == 1) && buswr) ? buswdata : 8'bzzzzzzzz;
	assign busdata = (bus == 0) ? bus0data : bus1data;
	assign bus0rd = (bus == 0) ? busrd : 1'b0;
	assign bus1rd = (bus == 1) ? busrd : 1'b0;
	assign bus0wr = (bus == 0) ? buswr : 1'b0;
	assign bus1wr = (bus == 1) ? buswr : 1'b0;

	reg ie, iedelay;

	wire [7:0] rlc,rrc,rl,rr,sla,sra,swap,srl;
	wire [3:0] rlcf,rrcf,rlf,rrf,slaf,sraf,swapf,srlf;
	wire [7:0] alu_res;
	wire [3:0] f_res;

	assign rlc   = {tmp[6:0],tmp[7]};
	assign rlcf  = {(tmp == 0 ? 1'b1 : 1'b0)
			,2'b0,
			tmp[7]};

	assign rrc   = {tmp[0],tmp[7:1]};
	assign rrcf  = {(tmp == 0 ? 1'b1 : 1'b0),
			2'b0,
			tmp[0]};

	assign rl    = {tmp[6:0],`_F[4]};
	assign rlf   = {({tmp[6:0],`_F[4]} == 0 ? 1'b1 : 1'b0),
			2'b0,
			tmp[7]};

	assign rr    = {`_F[4],tmp[7:1]};
	assign rrf   = {({tmp[4],tmp[7:1]} == 0 ? 1'b1 : 1'b0),
			2'b0,
			tmp[0]};

	assign sla   = {tmp[6:0],1'b0};
	assign slaf  = {(tmp[6:0] == 0 ? 1'b1 : 1'b0),
			2'b0,
			tmp[7]};

	assign sra   = {tmp[7],tmp[7:1]};
//	assign sraf  = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),2'b0,tmp[0]};   now in assign srlf =

	assign swap  = {tmp[3:0],tmp[7:4]};
	assign swapf = {(tmp == 1'b0 ? 1'b1 : 1'b0),
			3'b0};

	assign srl   = {1'b0,tmp[7:1]};
	assign srlf  = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),
			2'b0,
			tmp[0]};
	assign sraf  = srlf;

	/*  Y U Q  */
	assign {alu_res,f_res} =
		opcode[5] ? (
			opcode[4] ? (
				opcode[3] ? {srl,srlf} : {swap,swapf}
			) : (
				opcode[3] ? {sra,sraf} : {sla,slaf}
			)
		) : (
			opcode[4] ? (
				opcode[3] ? {rr,rrf} : {rl,rlf}
			) : (
				opcode[3] ? {rrc,rrcf} : {rlc,rlcf}
			)
		);

	initial begin
		`_A <= 0;
		`_B <= 0;
		`_C <= 0;
		`_D <= 0;
		`_E <= 0;
		`_F <= 0;
		`_H <= 0;
		`_L <= 0;
		`_PCH <= 0;
		`_PCL <= 0;
		`_SPH <= 0;
		`_SPL <= 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;
		twobyte <= 0;
		bootstrap_enb <= 1;
		irqack <= 0;
	end

	always @(negedge clk)	/* Set things up at the negedge to prepare for the posedge. */
		case (state)
		`STATE_FETCH: begin
			if (newcycle) begin
				busaddress <= `_PC;
				buswr <= 0;
				busrd <= 1;
			end else begin
				busaddress <= address;
				buswr <= wr;
				busrd <= rd;
				if (wr) begin
					buswdata <= wdata;
					if (address == 16'hFF50)
						bootstrap_enb <= 0;
				end
			end
		end
		`STATE_DECODE: begin	/* Make sure this only happens for one clock. */
			buswr <= 0;
			busrd <= 0;
		end
		endcase
	
	always @(posedge clk)
		case (state)
		`STATE_FETCH: begin
			/* Things are set up in negedge so that something looking on posedge will get his shit. */
			state <= `STATE_DECODE;
		end
		`STATE_DECODE: begin
			if (newcycle) begin
				if (twobyte) begin
					opcode <= {1'b1,busdata};
					twobyte <= 0;
				end else if (ie && irq)
					opcode <= `INSN_VOP_INTR;
				else
					opcode <= {1'b0,busdata};
				newcycle <= 0;
				rdata <= busdata;
				cycle <= 0;
			end else begin
				if (rd) rdata <= busdata;	/* Still valid because peripherals are now expected to keep it held valid. */
				cycle <= cycle + 1;
			end
			if (iedelay) begin
				ie <= 1;
				iedelay <= 0;
			end
			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
		`ifdef isim
			if (opcode[7:0] === 8'bxxxxxxxx)
				$stop;
		`endif
			casex (opcode)
			`define EXECUTE
			`include "allinsns.v"
			`undef EXECUTE
			default:
				$stop;
			endcase
			state <= `STATE_WRITEBACK;
		end
		`STATE_WRITEBACK: begin
			casex (opcode)
			`define WRITEBACK
			`include "allinsns.v"
			`undef WRITEBACK
			default:
				$stop;
			endcase
			state <= `STATE_FETCH;
		end
		endcase
endmodule
Commit	Line	Data
df770340 JW	1	`define REG_A 0
	2	`define REG_B 1
	3	`define REG_C 2
	4	`define REG_D 3
	5	`define REG_E 4
	6	`define REG_F 5
	7	`define REG_H 6
	8	`define REG_L 7
	9	`define REG_SPH 8
	10	`define REG_SPL 9
	11	`define REG_PCH 10
	12	`define REG_PCL 11
2f55f809	13
5509558d JW	14	`define _A registers[`REG_A]
	15	`define _B registers[`REG_B]
	16	`define _C registers[`REG_C]
	17	`define _D registers[`REG_D]
	18	`define _E registers[`REG_E]
	19	`define _F registers[`REG_F]
	20	`define _H registers[`REG_H]
	21	`define _L registers[`REG_L]
	22	`define _SPH registers[`REG_SPH]
	23	`define _SPL registers[`REG_SPL]
	24	`define _PCH registers[`REG_PCH]
	25	`define _PCL registers[`REG_PCL]
	26	`define _AF {`_A, `_F}
	27	`define _BC {`_B, `_C}
	28	`define _DE {`_D, `_E}
	29	`define _HL {`_H, `_L}
	30	`define _SP {`_SPH, `_SPL}
	31	`define _PC {`_PCH, `_PCL}
	32
df770340 JW	33	`define FLAG_Z 8'b10000000
	34	`define FLAG_N 8'b01000000
	35	`define FLAG_H 8'b00100000
	36	`define FLAG_C 8'b00010000
2f55f809	37
df770340 JW	38	`define STATE_FETCH 2'h0
df770340 JW	39	`define STATE_DECODE 2'h1
2f55f809 JW	40	`define STATE_EXECUTE 2'h2
	41	`define STATE_WRITEBACK 2'h3
	42
decafd62 JW	43	`define INSN_LD_reg_imm8 9'b000xxx110
	44	`define INSN_HALT 9'b001110110
	45	`define INSN_LD_HL_reg 9'b001110xxx
	46	`define INSN_LD_reg_HL 9'b001xxx110
	47	`define INSN_LD_reg_reg 9'b001xxxxxx
	48	`define INSN_LD_reg_imm16 9'b000xx0001
	49	`define INSN_LD_SP_HL 9'b011111001
	50	`define INSN_PUSH_reg 9'b011xx0101
	51	`define INSN_POP_reg 9'b011xx0001
	52	`define INSN_LDH_AC 9'b0111x0010 // Either LDH A,(C) or LDH (C),A
	53	`define INSN_LDx_AHL 9'b0001xx010 // LDD/LDI A,(HL) / (HL),A
	54	`define INSN_ALU8 9'b010xxxxxx // 10 xxx yyy
	55	`define INSN_ALU8IMM 9'b011xxx110
	56	`define INSN_NOP 9'b000000000
	57	`define INSN_RST 9'b011xxx111
	58	`define INSN_RET 9'b0110x1001 // 1 = RETI, 0 = RET
	59	`define INSN_RETCC 9'b0110xx000
	60	`define INSN_CALL 9'b011001101
	61	`define INSN_CALLCC 9'b0110xx100 // Not that call/cc.
	62	`define INSN_JP_imm 9'b011000011
	63	`define INSN_JPCC_imm 9'b0110xx010
	64	`define INSN_ALU_A 9'b000xxx111
	65	`define INSN_JP_HL 9'b011101001
	66	`define INSN_JR_imm 9'b000011000
	67	`define INSN_JRCC_imm 9'b0001xx000
	68	`define INSN_INCDEC16 9'b000xxx011
	69	`define INSN_VOP_INTR 9'b011111100 // 0xFC is grabbed by the fetch if there is an interrupt pending.
	70	`define INSN_DI 9'b011110011
	71	`define INSN_EI 9'b011111011
	72	`define INSN_INCDEC_HL 9'b00011010x
	73	`define INSN_INCDEC_reg8 9'b000xxx10x
	74	`define INSN_LD8M_A 9'b0111x0000 // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
	75	`define INSN_LD16M_A 9'b0111x1010 // 1111 for ld A, x; 1110 for ld x, A; bit 1 specifies 16m8 or 8m8
	76	`define INSN_LDBCDE_A 9'b0000xx010
	77	`define INSN_TWO_BYTE 9'b011001011 // prefix for two-byte opqodes
	78	`define INSN_ALU_EXT 9'b100xxxxxx
	79	`define INSN_BIT 9'b101xxxxxx
	80	`define INSN_RES 9'b110xxxxxx
	81	`define INSN_SET 9'b111xxxxxx
00a4c19f	82	`define INSN_ADD_HL 9'b000xx1001
a85b19a7	83
df770340 JW	84	`define INSN_cc_NZ 2'b00
	85	`define INSN_cc_Z 2'b01
	86	`define INSN_cc_NC 2'b10
	87	`define INSN_cc_C 2'b11
fa136d63	88
b85870e0 JW	89	`define INSN_reg_A 3'b111
	90	`define INSN_reg_B 3'b000
	91	`define INSN_reg_C 3'b001
	92	`define INSN_reg_D 3'b010
	93	`define INSN_reg_E 3'b011
	94	`define INSN_reg_H 3'b100
	95	`define INSN_reg_L 3'b101
df770340 JW	96	`define INSN_reg_dHL 3'b110
	97	`define INSN_reg16_BC 2'b00
	98	`define INSN_reg16_DE 2'b01
	99	`define INSN_reg16_HL 2'b10
	100	`define INSN_reg16_SP 2'b11
	101	`define INSN_stack_AF 2'b11
	102	`define INSN_stack_BC 2'b00
	103	`define INSN_stack_DE 2'b01
	104	`define INSN_stack_HL 2'b10
94522011 JW	105	`define INSN_alu_ADD 3'b000
	106	`define INSN_alu_ADC 3'b001
	107	`define INSN_alu_SUB 3'b010
	108	`define INSN_alu_SBC 3'b011
	109	`define INSN_alu_AND 3'b100
	110	`define INSN_alu_XOR 3'b101
	111	`define INSN_alu_OR 3'b110
	112	`define INSN_alu_CP 3'b111 // Oh lawd, is dat some CP?
a00483d0 JW	113	`define INSN_alu_RLCA 3'b000
	114	`define INSN_alu_RRCA 3'b001
	115	`define INSN_alu_RLA 3'b010
	116	`define INSN_alu_RRA 3'b011
	117	`define INSN_alu_DAA 3'b100
	118	`define INSN_alu_CPL 3'b101
	119	`define INSN_alu_SCF 3'b110
	120	`define INSN_alu_CCF 3'b111
decafd62 JW	121	`define INSN_alu_RLC 3'b000
	122	`define INSN_alu_RRC 3'b001
	123	`define INSN_alu_RL 3'b010
	124	`define INSN_alu_RR 3'b011
	125	`define INSN_alu_DA_SLA 3'b100
	126	`define INSN_alu_CPL_SRA 3'b101
	127	`define INSN_alu_SCF_SWAP 3'b110
	128	`define INSN_alu_CCF_SRL 3'b111
94522011	129
5c33c5c0 JW	130	`define EXEC_INC_PC `_PC <= `_PC + 1;
	131	`define EXEC_NEXTADDR_PCINC address <= `_PC + 1;
	132	`define EXEC_NEWCYCLE begin newcycle <= 1; rd <= 1; wr <= 0; end
decafd62	133	`define EXEC_NEWCYCLE_TWOBYTE begin newcycle <= 1; rd <= 1; wr <= 0; twobyte <= 1; end
e7fb589a JW	134	`ifdef verilator
	135	`define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end
	136	`define EXEC_READ(ad) begin address <= (ad); rd <= 1; end
	137	`else
	138	`ifdef isim
	139	`define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end
	140	`define EXEC_READ(ad) begin address <= (ad); rd <= 1; end
	141	`else
	142	/* Work around XST's retarded bugs :\ */
	143	`define EXEC_WRITE(ad, da) begin address <= (ad); wdata <= (da); wr <= 1; end end
	144	`define EXEC_READ(ad) begin address <= (ad); rd <= 1; end end
	145	`endif
	146	`endif
5509558d	147
2f55f809 JW	148	module GBZ80Core(
2f55f809 JW	149	input clk,
91c74a3f JW	150	inout [15:0] bus0address, /* BUS_* is latched on STATE_FETCH. */
	151	inout [7:0] bus0data,
	152	inout bus0wr, bus0rd,
	153	inout [15:0] bus1address, /* BUS_* is latched on STATE_FETCH. */
	154	inout [7:0] bus1data,
	155	inout bus1wr, bus1rd,
d1b40456	156	input irq, output reg irqack, input [7:0] jaddr,
6c46357c	157	output reg [1:0] state);
decafd62	158
6c46357c	159	// reg [1:0] state; /* State within this bus cycle (see STATE_). /
9c834ff2	160	reg [2:0] cycle; /* Cycle for instructions. */
2f55f809 JW	161
	162	reg [7:0] registers[11:0];
	163
	164	reg [15:0] address; /* Address for the next bus operation. */
	165
decafd62 JW	166	reg [8:0] opcode; /* Opcode from the current machine cycle. */
decafd62 JW	167
2f55f809	168	reg [7:0] rdata, wdata; /* Read data from this bus cycle, or write data for the next. */
decafd62	169	reg rd, wr, newcycle, twobyte;
2f55f809	170
ef6fbe31	171	reg [7:0] tmp, tmp2; /* Generic temporary regs. */
b85870e0	172
2f55f809	173	reg [7:0] buswdata;
91c74a3f JW	174	wire [7:0] busdata;
	175
	176	reg [15:0] busaddress;
	177	reg buswr, busrd;
	178
	179	reg bootstrap_enb;
	180
e29171aa JW	181	wire bus = ((busaddress[15:8] == 8'h00) && bootstrap_enb) \|\| ((busaddress[15:7] == 9'b111111111) && (busaddress != 16'hFFFF)) /* 0 or 1 depending on which bus */
	182	`ifdef isim
	183	\|\| (busaddress === 16'hxxxx) /* To avoid simulator glomulation. */
	184	`endif
	185	;
91c74a3f JW	186
	187	assign bus0address = (bus == 0) ? busaddress : 16'bzzzzzzzzzzzzzzz;
	188	assign bus1address = (bus == 1) ? busaddress : 16'bzzzzzzzzzzzzzzz;
	189	assign bus0data = ((bus == 0) && buswr) ? buswdata : 8'bzzzzzzzz;
	190	assign bus1data = ((bus == 1) && buswr) ? buswdata : 8'bzzzzzzzz;
	191	assign busdata = (bus == 0) ? bus0data : bus1data;
e29171aa JW	192	assign bus0rd = (bus == 0) ? busrd : 1'b0;
	193	assign bus1rd = (bus == 1) ? busrd : 1'b0;
	194	assign bus0wr = (bus == 0) ? buswr : 1'b0;
	195	assign bus1wr = (bus == 1) ? buswr : 1'b0;
decafd62	196
eb0f2fe1	197	reg ie, iedelay;
decafd62 JW	198
	199	wire [7:0] rlc,rrc,rl,rr,sla,sra,swap,srl;
	200	wire [3:0] rlcf,rrcf,rlf,rrf,slaf,sraf,swapf,srlf;
	201	wire [7:0] alu_res;
	202	wire [3:0] f_res;
	203
	204	assign rlc = {tmp[6:0],tmp[7]};
	205	assign rlcf = {(tmp == 0 ? 1'b1 : 1'b0)
	206	,2'b0,
	207	tmp[7]};
	208
	209	assign rrc = {tmp[0],tmp[7:1]};
	210	assign rrcf = {(tmp == 0 ? 1'b1 : 1'b0),
	211	2'b0,
	212	tmp[0]};
	213
	214	assign rl = {tmp[6:0],`_F[4]};
	215	assign rlf = {({tmp[6:0],`_F[4]} == 0 ? 1'b1 : 1'b0),
	216	2'b0,
	217	tmp[7]};
	218
	219	assign rr = {`_F[4],tmp[7:1]};
	220	assign rrf = {({tmp[4],tmp[7:1]} == 0 ? 1'b1 : 1'b0),
	221	2'b0,
	222	tmp[0]};
	223
e7fb589a	224	assign sla = {tmp[6:0],1'b0};
decafd62 JW	225	assign slaf = {(tmp[6:0] == 0 ? 1'b1 : 1'b0),
	226	2'b0,
	227	tmp[7]};
	228
	229	assign sra = {tmp[7],tmp[7:1]};
	230	// assign sraf = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),2'b0,tmp[0]}; now in assign srlf =
	231
	232	assign swap = {tmp[3:0],tmp[7:4]};
e7fb589a	233	assign swapf = {(tmp == 1'b0 ? 1'b1 : 1'b0),
decafd62 JW	234	3'b0};
decafd62 JW	235
e7fb589a	236	assign srl = {1'b0,tmp[7:1]};
decafd62 JW	237	assign srlf = {(tmp[7:1] == 0 ? 1'b1 : 1'b0),
	238	2'b0,
	239	tmp[0]};
	240	assign sraf = srlf;
	241
	242	/* Y U Q */
	243	assign {alu_res,f_res} =
	244	opcode[5] ? (
	245	opcode[4] ? (
	246	opcode[3] ? {srl,srlf} : {swap,swapf}
	247	) : (
	248	opcode[3] ? {sra,sraf} : {sla,slaf}
	249	)
	250	) : (
	251	opcode[4] ? (
	252	opcode[3] ? {rr,rrf} : {rl,rlf}
	253	) : (
	254	opcode[3] ? {rrc,rrcf} : {rlc,rlcf}
	255	)
	256	);
	257
2f55f809	258	initial begin
b4f3ac35 JW	259	`_A <= 0;
	260	`_B <= 0;
	261	`_C <= 0;
	262	`_D <= 0;
	263	`_E <= 0;
	264	`_F <= 0;
	265	`_H <= 0;
	266	`_L <= 0;
	267	`_PCH <= 0;
	268	`_PCL <= 0;
	269	`_SPH <= 0;
	270	`_SPL <= 0;
2e642f1f JW	271	rd <= 1;
	272	wr <= 0;
	273	newcycle <= 1;
	274	state <= 0;
	275	cycle <= 0;
f8db6448 JW	276	busrd <= 0;
	277	buswr <= 0;
	278	busaddress <= 0;
9c834ff2	279	ie <= 0;
f8db6448	280	iedelay <= 0;
9c834ff2 JW	281	opcode <= 0;
	282	state <= `STATE_WRITEBACK;
	283	cycle <= 0;
decafd62	284	twobyte <= 0;
91c74a3f	285	bootstrap_enb <= 1;
d1b40456	286	irqack <= 0;
2f55f809 JW	287	end
2f55f809 JW	288
b338a0b6	289	always @(negedge clk) /* Set things up at the negedge to prepare for the posedge. */
2f55f809 JW	290	case (state)
2f55f809 JW	291	`STATE_FETCH: begin
2e642f1f	292	if (newcycle) begin
decafd62	293	busaddress <= `_PC;
2e642f1f JW	294	buswr <= 0;
	295	busrd <= 1;
	296	end else begin
2f55f809	297	busaddress <= address;
2e642f1f JW	298	buswr <= wr;
2e642f1f JW	299	busrd <= rd;
1eefdc8e	300	if (wr) begin
2e642f1f	301	buswdata <= wdata;
1eefdc8e JW	302	if (address == 16'hFF50)
	303	bootstrap_enb <= 0;
	304	end
2e642f1f	305	end
b338a0b6 JW	306	end
b338a0b6 JW	307	`STATE_DECODE: begin /* Make sure this only happens for one clock. */
e29171aa JW	308	buswr <= 0;
e29171aa JW	309	busrd <= 0;
b338a0b6 JW	310	end
	311	endcase
	312
	313	always @(posedge clk)
	314	case (state)
	315	`STATE_FETCH: begin
	316	/* Things are set up in negedge so that something looking on posedge will get his shit. */
2f55f809 JW	317	state <= `STATE_DECODE;
	318	end
	319	`STATE_DECODE: begin
	320	if (newcycle) begin
decafd62	321	if (twobyte) begin
e7fb589a	322	opcode <= {1'b1,busdata};
decafd62 JW	323	twobyte <= 0;
decafd62 JW	324	end else if (ie && irq)
f8db6448 JW	325	opcode <= `INSN_VOP_INTR;
f8db6448 JW	326	else
e7fb589a	327	opcode <= {1'b0,busdata};
b85870e0	328	newcycle <= 0;
2854e399	329	rdata <= busdata;
2f55f809	330	cycle <= 0;
2e642f1f	331	end else begin
e29171aa	332	if (rd) rdata <= busdata; /* Still valid because peripherals are now expected to keep it held valid. */
2e642f1f JW	333	cycle <= cycle + 1;
2e642f1f JW	334	end
f8db6448 JW	335	if (iedelay) begin
	336	ie <= 1;
	337	iedelay <= 0;
	338	end
97649fed JW	339	wr <= 0;
	340	rd <= 0;
	341	address <= 16'bxxxxxxxxxxxxxxxx; // Make it obvious if something of type has happened.
	342	wdata <= 8'bxxxxxxxx;
2f55f809 JW	343	state <= `STATE_EXECUTE;
	344	end
	345	`STATE_EXECUTE: begin
d1b40456	346	`ifdef isim
e29171aa JW	347	if (opcode[7:0] === 8'bxxxxxxxx)
e29171aa JW	348	$stop;
d1b40456	349	`endif
2f55f809	350	casex (opcode)
81358c71 JW	351	`define EXECUTE
	352	`include "allinsns.v"
	353	`undef EXECUTE
634ce02c JW	354	default:
634ce02c JW	355	$stop;
2f55f809 JW	356	endcase
	357	state <= `STATE_WRITEBACK;
	358	end
	359	`STATE_WRITEBACK: begin
	360	casex (opcode)
81358c71 JW	361	`define WRITEBACK
	362	`include "allinsns.v"
	363	`undef WRITEBACK
ef6fbe31 JW	364	default:
ef6fbe31 JW	365	$stop;
2f55f809 JW	366	endcase
	367	state <= `STATE_FETCH;
	368	end
	369	endcase
	370	endmodule