Cut 1 at interrupt support for CPU
authorJoshua Wise <joshua@rebirth.joshuawise.com>
Sat, 5 Apr 2008 04:34:42 +0000 (00:34 -0400)
committerJoshua Wise <joshua@rebirth.joshuawise.com>
Sat, 5 Apr 2008 04:34:42 +0000 (00:34 -0400)
FPGABoy.ise
GBZ80Core.v
System.v

index 2278455..3562e29 100644 (file)
Binary files a/FPGABoy.ise and b/FPGABoy.ise differ
index 095d9e8..57c22d2 100644 (file)
@@ -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
index 8b8d613..7319ebf 100644 (file)
--- 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),
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