Dual boot ROM support, and the first proof that cellular ram works!

[fpgaboy.git] / GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 45870d195f581fc91d2fe6617f1200789f3ab98c..e1aa3087b0a94f4cb7e422c3160b7849bf334c5a 100644 (file)
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -130,14 +130,28 @@
 `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
 `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

-`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
+`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,
 
 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,
+       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, input [7:0] jaddr,
        output reg [1:0] state);
 
        input irq, input [7:0] jaddr,
        output reg [1:0] state);
 


@@ -156,7 +170,28 @@ module GBZ80Core(
        reg [7:0] tmp, tmp2;                    /* Generic temporary regs. */
        
        reg [7:0] buswdata;
        reg [7:0] tmp, tmp2;                    /* Generic temporary regs. */
        
        reg [7:0] buswdata;

-       assign busdata = buswr ? buswdata : 8'bzzzzzzzz;
+       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;
 
 
        reg ie, iedelay;
 


@@ -185,7 +220,7 @@ module GBZ80Core(
                        2'b0,
                        tmp[0]};
 
                        2'b0,
                        tmp[0]};
 

-       assign sla   = {tmp[6:0],0};
+       assign sla   = {tmp[6:0],1'b0};

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


@@ -194,10 +229,10 @@ module GBZ80Core(
 //     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 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 == 0 ? 1'b1 : 1'b0),
+       assign swapf = {(tmp == 1'b0 ? 1'b1 : 1'b0),

                        3'b0};
 
                        3'b0};
 

-       assign srl   = {0,tmp[7:1]};
+       assign srl   = {1'b0,tmp[7:1]};

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


@@ -220,18 +255,18 @@ module GBZ80Core(
                );
 
        initial begin
                );
 
        initial begin

-               registers[ 0] <= 0;
-               registers[ 1] <= 0;
-               registers[ 2] <= 0;
-               registers[ 3] <= 0;
-               registers[ 4] <= 0;
-               registers[ 5] <= 0;
-               registers[ 6] <= 0;
-               registers[ 7] <= 0;
-               registers[ 8] <= 0;
-               registers[ 9] <= 0;
-               registers[10] <= 0;
-               registers[11] <= 0;
+               `_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;
                rd <= 1;
                wr <= 0;
                newcycle <= 1;


@@ -246,9 +281,10 @@ module GBZ80Core(
                state <= `STATE_WRITEBACK;
                cycle <= 0;
                twobyte <= 0;
                state <= `STATE_WRITEBACK;
                cycle <= 0;
                twobyte <= 0;

+               bootstrap_enb <= 1;

        end
 
        end
 

-       always @(posedge clk)
+       always @(negedge clk)   /* Set things up at the negedge to prepare for the posedge. */

                case (state)
                `STATE_FETCH: begin
                        if (newcycle) begin
                case (state)
                `STATE_FETCH: begin
                        if (newcycle) begin


@@ -262,30 +298,39 @@ module GBZ80Core(
                                if (wr)
                                        buswdata <= wdata;
                        end
                                if (wr)
                                        buswdata <= wdata;
                        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
                        state <= `STATE_DECODE;
                end
                `STATE_DECODE: begin
                        if (newcycle) begin
                                if (twobyte) begin

-                                       opcode <= {1,busdata};
+                                       opcode <= {1'b1,busdata};

                                        twobyte <= 0;
                                end else if (ie && irq)
                                        opcode <= `INSN_VOP_INTR;
                                else
                                        twobyte <= 0;
                                end else if (ie && irq)
                                        opcode <= `INSN_VOP_INTR;
                                else

-                                       opcode <= {0,busdata};
-                               rdata <= busdata;
+                                       opcode <= {1'b0,busdata};

                                newcycle <= 0;
                                newcycle <= 0;

+                               rdata <= busdata;

                                cycle <= 0;
                        end else begin
                                cycle <= 0;
                        end else begin

-                               if (rd) rdata <= busdata;
+                               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
                                cycle <= cycle + 1;
                        end
                        if (iedelay) begin
                                ie <= 1;
                                iedelay <= 0;
                        end

-                       buswr <= 0;
-                       busrd <= 0;

                        wr <= 0;
                        rd <= 0;
                        address <= 16'bxxxxxxxxxxxxxxxx;        // Make it obvious if something of type has happened.
                        wr <= 0;
                        rd <= 0;
                        address <= 16'bxxxxxxxxxxxxxxxx;        // Make it obvious if something of type has happened.


@@ -293,6 +338,8 @@ module GBZ80Core(
                        state <= `STATE_EXECUTE;
                end
                `STATE_EXECUTE: begin
                        state <= `STATE_EXECUTE;
                end
                `STATE_EXECUTE: begin

+                       if (opcode[7:0] === 8'bxxxxxxxx)
+                               $stop;

                        casex (opcode)
                        `define EXECUTE
                        `include "allinsns.v"
                        casex (opcode)
                        `define EXECUTE
                        `include "allinsns.v"