From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Sat, 5 Apr 2008 04:34:42 +0000 (-0400)
Subject: Cut 1 at interrupt support for CPU
X-Git-Url: http://git.joshuawise.com/fpgaboy.git/commitdiff_plain/f8db64484a25b6970acb75b35188efd7089e572a

Cut 1 at interrupt support for CPU
---

diff --git a/FPGABoy.ise b/FPGABoy.ise
index 2278455..3562e29 100644
Binary files a/FPGABoy.ise and b/FPGABoy.ise differ
diff --git a/GBZ80Core.v b/GBZ80Core.v
index 095d9e8..57c22d2 100644
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -46,6 +46,9 @@
 `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
@@ -89,7 +92,8 @@ module GBZ80Core(
 	input clk,
 	output reg [15:0] busaddress = 0,	/* BUS_* is latched on STATE_FETCH. */
 	inout [7:0] busdata,
-	output reg buswr = 0, output reg busrd = 0);
+	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. */
@@ -108,7 +112,7 @@ module GBZ80Core(
 	reg [7:0] buswdata;
 	assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
 	
-	reg ie = 0;
+	reg ie = 0, iedelay = 0;
 	
 	initial begin
 		registers[ 0] <= 0;
@@ -129,6 +133,10 @@ module GBZ80Core(
 		newcycle <= 1;
 		state <= 0;
 		cycle <= 0;
+		busrd <= 0;
+		buswr <= 0;
+		busaddress <= 0;
+		iedelay <= 0;
 	end
 
 	always @(posedge clk)
@@ -149,7 +157,10 @@ 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;
@@ -157,6 +168,10 @@ module GBZ80Core(
 				if (rd) rdata <= busdata;
 				cycle <= cycle + 1;
 			end
+			if (iedelay) begin
+				ie <= 1;
+				iedelay <= 0;
+			end
 			buswr <= 0;
 			busrd <= 0;
 			wr <= 0;
@@ -552,6 +567,31 @@ module GBZ80Core(
 					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
@@ -896,6 +936,20 @@ module GBZ80Core(
 					end
 				endcase
 			end
+			`INSN_VOP_INTR: begin
+				case (cycle)
+				0:	begin end
+				1:	{registers[`REG_SPH],registers[`REG_SPL]}
+						<= {registers[`REG_SPH],registers[`REG_SPL]} - 2;
+				2:	begin
+						ie <= 0;
+						{registers[`REG_PCH],registers[`REG_PCL]} <=
+							{8'b0,jaddr};
+					end
+				endcase
+			end
+			`INSN_DI: ie <= 0;
+			`INSN_EI: iedelay <= 1;
 			default:
 				$stop;
 			endcase
diff --git a/System.v b/System.v
index 8b8d613..7319ebf 100644
--- a/System.v
+++ b/System.v
@@ -76,13 +76,18 @@ module CoreTop(
 	wire [15:0] addr;	
 	wire [7:0] data;
 	wire wr, rd;
+	
+	wire irq, tmrirq;
+	wire [7:0] jaddr;
 
 	GBZ80Core core(
 		.clk(clk),
 		.busaddress(addr),
 		.busdata(data),
 		.buswr(wr),
-		.busrd(rd));
+		.busrd(rd),
+		.irq(irq),
+		.jaddr(jaddr));
 	
 	ROM rom(
 		.address(addr),
@@ -125,8 +130,6 @@ module CoreTop(
 		.wr(wr),
 		.rd(rd));
 
-	wire irq, tmrirq;
-	wire [7:0] jaddr;
 	Timer tmr(
 		.clk(clk),
 		.wr(wr),
@@ -156,6 +159,9 @@ module TestBench();
 	wire [7:0] data;
 	wire wr, rd;
 	
+	wire irq, tmrirq;
+	wire [7:0] jaddr;
+	
 //	wire [7:0] leds;
 //	wire [7:0] switches;
 	
@@ -165,7 +171,9 @@ module TestBench();
 		.busaddress(addr),
 		.busdata(data),
 		.buswr(wr),
-		.busrd(rd));
+		.busrd(rd),
+		.irq(irq),
+		.jaddr(jaddr));
 	
 	ROM rom(
 		.clk(clk),
@@ -190,8 +198,6 @@ module TestBench();
 		.rd(rd),
 		.serial(serio));
 	
-	wire irq, tmrirq;
-	wire [7:0] jaddr;
 	Timer tmr(
 		.clk(clk),
 		.wr(wr),