Dual bus processor

[fpgaboy.git] / GBZ80Core.v

diff --git a/GBZ80Core.v b/GBZ80Core.v
index 1182b327709e7d4cd3fc24e52fd2a128cd46d1c1..ec882da4d7841ee789180cd0ea85138843cfbc95 100644 (file)
--- a/GBZ80Core.v
+++ b/GBZ80Core.v
@@ -146,9 +146,12 @@
 
 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);
 
@@ -167,7 +170,24 @@ module GBZ80Core(
        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 */
+               
+       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'bz;
+       assign bus1rd = (bus == 1) ? busrd : 1'bz;
+       assign bus0wr = (bus == 0) ? buswr : 1'bz;
+       assign bus1wr = (bus == 1) ? buswr : 1'bz;
 
        reg ie, iedelay;
 
@@ -257,6 +277,7 @@ module GBZ80Core(
                state <= `STATE_WRITEBACK;
                cycle <= 0;
                twobyte <= 0;
+               bootstrap_enb <= 1;
        end
 
        always @(posedge clk)