Make the boot rom talk a bit more, and wait for you to flip a switch. Make the 'progr...

[fpgaboy.git] / System.v

diff --git a/System.v b/System.v
index b1d4c3d90241b3aaab8ac4f103e1dbf292c177b9..62683d3bbd5b2b69809da5f0ec33b112f08a054d 100644 (file)
--- a/System.v
+++ b/System.v
@@ -29,14 +29,20 @@ module BootstrapROM(
 
        reg rdlatch = 0;
        reg [7:0] addrlatch = 0;
-       reg [7:0] brom [255:0];
-       initial $readmemh("bootstrap.hex", brom);
+       reg romno = 0, romnotmp = 0;
+       reg [7:0] brom0 [255:0];
+       reg [7:0] brom1 [255:0];
+       
+       initial $readmemh("fpgaboot.hex", brom0);
+       initial $readmemh("gbboot.hex", brom1);
 
        wire decode = address[15:8] == 0;
-       wire [7:0] odata = brom[addrlatch];
+       wire [7:0] odata = (romno == 0) ? brom0[addrlatch] : brom1[addrlatch];
        always @(posedge clk) begin
                rdlatch <= rd && decode;
                addrlatch <= address[7:0];
+               if (wr && decode) romnotmp <= data[0];
+               if (rd && address == 16'h0000) romno <= romnotmp;       /* Latch when the program restarts. */
        end
        assign data = rdlatch ? odata : 8'bzzzzzzzz;
 endmodule
@@ -86,6 +92,8 @@ module CellularRAM(
        
        reg [7:0] progaddrh, progaddrm, progaddrl;
        
+       reg [22:0] progaddr;
+       
        assign cr_nADV = 0;     /* Addresses are always valid! :D */
        assign cr_nCE = 0;      /* The chip is enabled */
        assign cr_nLB = 0;      /* Lower byte is enabled */
@@ -101,7 +109,7 @@ module CellularRAM(
        assign cr_DQ = (~cr_nOE) ? 16'bzzzzzzzzzzzzzzzz : {8'b0, datalatch};
        assign cr_A = (addrlatch[15:14] == 2'b00) ? /* extrom */ {9'b0,addrlatch[13:0]} :
                        (addrlatch[15:13] == 3'b101) ? {1'b1, 9'b0, addrlatch[12:0]} :
-                       (addrlatch == ADDR_PROGDATA) ? {progaddrh[6:0], progaddrm[7:0], progaddrl[7:0]} :
+                       (addrlatch == ADDR_PROGDATA) ? progaddr :
                        23'b0;
        
        reg [7:0] regbuf;
@@ -111,6 +119,10 @@ module CellularRAM(
                ADDR_PROGADDRH: if (wr) progaddrh <= data;
                ADDR_PROGADDRM: if (wr) progaddrm <= data;
                ADDR_PROGADDRL: if (wr) progaddrl <= data;
+               ADDR_PROGDATA:  if (rd || wr) begin
+                                       progaddr <= {progaddrh[6:0], progaddrm[7:0], progaddr[7:0]};
+                                       {progaddrh[6:0], progaddrm[7:0], progaddr[7:0]} <= {progaddrh[6:0], progaddrm[7:0], progaddr[7:0]} + 23'b1;
+                               end
                endcase
                rdlatch <= rd;
                wrlatch <= wr;