X-Git-Url: http://git.joshuawise.com/fpgaboy.git/blobdiff_plain/a85b19a7c7e7fecb4e71c41b37fb30dabaf8bd14..9c834ff2149ba2b9b4db71a1bb6b974235c88273:/GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 1bc8f78..ae6ff00 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -36,9 +36,19 @@
 `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_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
@@ -69,15 +79,24 @@
 `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,
-	output reg [15:0] busaddress,	/* BUS_* is latched on STATE_FETCH. */
+	output reg [15:0] busaddress = 0,	/* BUS_* is latched on STATE_FETCH. */
 	inout [7:0] busdata,
-	output reg buswr, output reg busrd);
+	output reg buswr = 0, output reg busrd = 0,
+	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];
 	
@@ -86,14 +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 = 0, iedelay = 0;
 	
 	initial begin
 		registers[ 0] <= 0;
@@ -108,12 +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)
@@ -134,7 +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;
@@ -142,6 +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;
@@ -272,7 +305,7 @@ module GBZ80Core(
 					end
 				1:	begin
 						wr <= 1;
-						address <= {registers[`REG_SPH],registers[`REG_SPL]}-1;
+						address <= {registers[`REG_SPH],registers[`REG_SPL]}-2;
 						case (opcode[5:4])
 						`INSN_stack_AF:	wdata <= registers[`REG_F];
 						`INSN_stack_BC:	wdata <= registers[`REG_C];
@@ -280,7 +313,7 @@ module GBZ80Core(
 						`INSN_stack_HL:	wdata <= registers[`REG_L];
 						endcase
 					end
-				2:	begin /* TWIDDLE OUR FUCKING THUMBS! */ end
+				2:	begin /* Twiddle thumbs. */ end
 				3:	begin
 						`EXEC_NEWCYCLE;
 						`EXEC_INC_PC;
@@ -295,7 +328,7 @@ module GBZ80Core(
 					end
 				1:	begin
 						rd <= 1;
-						address <= {registers[`REG_SPH],registers[`REG_SPL]};
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} + 1;
 					end
 				2:	begin
 						`EXEC_NEWCYCLE;
@@ -357,6 +390,10 @@ module GBZ80Core(
 					endcase
 				end
 			end
+			`INSN_ALU_A: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
+			end
 			`INSN_NOP: begin
 				`EXEC_NEWCYCLE;
 				`EXEC_INC_PC;
@@ -383,24 +420,35 @@ 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
 				endcase
 			end
-			`INSN_CALL: begin
+			`INSN_CALL,`INSN_CALLCC: begin
 				case (cycle)
 				0:	begin
 						`EXEC_INC_PC;
@@ -414,6 +462,14 @@ module GBZ80Core(
 					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;
@@ -443,13 +499,14 @@ module GBZ80Core(
 						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_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
+							`INSN_cc_C:		if (~registers[`REG_F][4]) begin `EXEC_NEWCYCLE; end
 							endcase
 						end
 					end
@@ -458,6 +515,86 @@ module GBZ80Core(
 					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
+			`INSN_VOP_INTR: begin
+				case (cycle)
+				0:	begin
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 1;
+						wdata <= registers[`REG_PCH];
+						wr <= 1;
+					end
+				1:	begin
+						address <= {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+						wdata <= registers[`REG_PCL];
+						wr <= 1;
+					end
+				2:	begin
+						`EXEC_NEWCYCLE;
+					end
+				endcase
+			end
+			`INSN_DI: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
+			end
+			`INSN_EI: begin
+				`EXEC_NEWCYCLE;
+				`EXEC_INC_PC;
+			end
 			default:
 				$stop;
 			endcase
@@ -543,18 +680,16 @@ module GBZ80Core(
 			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;
+				0:	begin /* type F */ end
+				1:	begin /* type F */ end
 				2:	begin /* type F */ end
-				3:	begin /* type F */ end
+				3:	{registers[`REG_SPH],registers[`REG_SPL]} <=
+						{registers[`REG_SPH],registers[`REG_SPL]} - 2;
 				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 end
 				1:	begin
 						case (opcode[5:4])
 						`INSN_stack_AF:	registers[`REG_F] <= rdata;
@@ -562,8 +697,6 @@ module GBZ80Core(
 						`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])
@@ -572,6 +705,8 @@ module GBZ80Core(
 						`INSN_stack_DE:	registers[`REG_D] <= rdata;
 						`INSN_stack_HL:	registers[`REG_H] <= rdata;
 						endcase
+						{registers[`REG_SPH],registers[`REG_SPL]} <=
+							{registers[`REG_SPH],registers[`REG_SPL]} + 2;
 					end
 				endcase
 			end
@@ -622,6 +757,28 @@ module GBZ80Core(
 							  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;
@@ -649,11 +806,50 @@ module GBZ80Core(
 							  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
 			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
+			end
 			`INSN_NOP: begin /* NOP! */ end
 			`INSN_RST: begin
 				case (cycle)
@@ -664,20 +860,22 @@ 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
 			end
-			`INSN_CALL: begin
+			`INSN_CALL,`INSN_CALLCC: begin
 				case (cycle)
 				0:	begin /* type F */ end
 				1:	tmp <= rdata;	// tmp contains newpcl
@@ -700,6 +898,60 @@ module GBZ80Core(
 						{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
+			`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