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

[fpgaboy.git] / System.v

diff --git a/System.v b/System.v
index b1d4c3d90241b3aaab8ac4f103e1dbf292c177b9..8c4cf1ae2e2b786491b4e5a7082e007c24baf5e8 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