Add cut 1 of a cellram module
[fpgaboy.git] / System.v
index 8f54685..4d0ddbb 100644 (file)
--- a/System.v
+++ b/System.v
@@ -6,12 +6,15 @@ module ROM(
        input clk,
        input wr, rd);
 
+       reg [7:0] odata;
+
        // synthesis attribute ram_style of rom is block
        reg [7:0] rom [1023:0];
        initial $readmemh("rom.hex", rom);
 
        wire decode = address[15:13] == 0;
-       wire [7:0] odata = rom[address[10:0]];
+       always @(posedge clk)
+               odata <= rom[address[10:0]];
        assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
 endmodule
 
@@ -21,11 +24,11 @@ module BootstrapROM(
        input clk,
        input wr, rd);
 
-       reg [7:0] rom [255:0];
-       initial $readmemh("bootstrap.hex", rom);
+       reg [7:0] brom [255:0];
+       initial $readmemh("bootstrap.hex", brom);
 
        wire decode = address[15:8] == 0;
-       wire [7:0] odata = rom[address[7:0]];
+       wire [7:0] odata = brom[address[7:0]];
        assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
 endmodule
 
@@ -52,6 +55,57 @@ module MiniRAM(
        end
 endmodule
 
+module CellularRAM(
+       input clk,
+       input [15:0] address,
+       inout [7:0] data,
+       input wr, rd,
+       output wire cr_nADV, cr_nCE, cr_nOE, cr_nWE, cr_CRE, cr_nLB, cr_nUB, cr_CLK,
+       output wire [22:0] cr_A,
+       inout [15:0] cr_DQ);
+       
+       parameter ADDR_PROGADDRH = 16'hFF60;
+       parameter ADDR_PROGADDRM = 16'hFF61;
+       parameter ADDR_PROGADDRL = 16'hFF62;
+       parameter ADDR_PROGDATA = 16'hFF63;
+       
+       reg [7:0] progaddrh, progaddrm, progaddrl;
+       
+       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 */
+       assign cr_nUB = 0;      /* Upper byte is enabled */
+       assign cr_CRE = 0;      /* Data writes, not config */
+       assign cr_CLK = 0;      /* Clock? I think not! */
+       
+       wire decode = (address[15:14] == 2'b00) /* extrom */ || (address[15:13] == 3'b101) /* extram */ || (address == ADDR_PROGDATA);
+       
+       assign cr_nOE = decode ? ~rd : 1;
+       assign cr_nWE = decode ? ~wr : 1;
+       
+       assign cr_DQ = (~cr_nOE) ? 16'bzzzzzzzzzzzzzzzz : {8'b0, data};
+       assign cr_A = (address[15:14] == 2'b00) ? /* extrom */ {9'b0,address[13:0]} :
+                       (address[15:13] == 3'b101) ? {1'b1, 9'b0, address[12:0]} :
+                       (address == ADDR_PROGDATA) ? {progaddrh[6:0], progaddrm[7:0], progaddrl[7:0]} :
+                       23'b0;
+       
+       reg [7:0] regbuf;
+       
+       always @(posedge clk)
+               case (address)
+               ADDR_PROGADDRH: if (wr) progaddrh <= data;
+               ADDR_PROGADDRM: if (wr) progaddrm <= data;
+               ADDR_PROGADDRL: if (wr) progaddrl <= data;
+               endcase
+       
+       assign data = (rd && decode) ?
+                               (address == ADDR_PROGADDRH) ? progaddrh :
+                               (address == ADDR_PROGADDRM) ? progaddrm :
+                               (address == ADDR_PROGADDRL) ? progaddrl :
+                               cr_DQ
+                       : 8'bzzzzzzzz;
+endmodule
+
 module InternalRAM(
        input [15:0] address,
        inout [7:0] data,
@@ -61,14 +115,14 @@ module InternalRAM(
        // synthesis attribute ram_style of ram is block
        reg [7:0] ram [8191:0];
        
-       wire decode = address[15:13] == 3'b110;
+       wire decode = (address >= 16'hC000) && (address <= 16'hFDFF);   /* This includes echo RAM. */
        reg [7:0] odata;
        assign data = (rd && decode) ? odata : 8'bzzzzzzzz;
        
        always @(posedge clk)
        begin
-               if (decode)     // This has to go this way. The only way XST knows how to do
-               begin                           // block ram is chip select, write enable, and always
+               if (decode)             // This has to go this way. The only way XST knows how to do
+               begin                   // block ram is chip select, write enable, and always
                        if (wr)         // reading. "else if rd" does not cut it ...
                                ram[address[12:0]] <= data;
                        odata <= ram[address[12:0]];
@@ -114,6 +168,9 @@ module CoreTop(
        output serio,
        output wire [3:0] digits,
        output wire [7:0] seven,
+       output wire cr_nADV, cr_nCE, cr_nOE, cr_nWE, cr_CRE, cr_nLB, cr_nUB, cr_CLK,
+       output wire [22:0] cr_A,
+       inout [15:0] cr_DQ,
 `endif
        output wire hs, vs,
        output wire [2:0] r, g,
@@ -168,12 +225,31 @@ module CoreTop(
                .wr(wr[1]),
                .rd(rd[1]));
        
+`ifdef isim
        ROM rom(
                .address(addr[0]),
                .data(data[0]),
                .clk(clk),
                .wr(wr[0]),
                .rd(rd[0]));
+`else
+       CellularRAM cellram(
+               .address(addr[0]),
+               .data(data[0]),
+               .clk(clk),
+               .wr(wr[0]),
+               .rd(rd[0])
+               .cr_nADV(cr_nADV),
+               .cr_nCE(cr_nCE),
+               .cr_nOE(cr_nOE),
+               .cr_nWR(cr_nWE),
+               .cr_CRE(cr_CRE),
+               .cr_nLB(cr_nLB),
+               .cr_nUB(cr_nUB),
+               .cr_CLK(cr_CLK),
+               .cr_A(cr_A),
+               .cr_DQ(cr_DQ));
+`endif
        
        wire lcdhs, lcdvs, lcdclk;
        wire [2:0] lcdr, lcdg;
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