From 74610a872e3bead82589e6ea786e928f319540e4 Mon Sep 17 00:00:00 2001
From: Joshua Wise <joshua@rebirth.joshuawise.com>
Date: Tue, 6 May 2008 05:01:40 -0400
Subject: [PATCH] Add cut 1 of a cellram module

---
 System.v | 79 +++++++++++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 76 insertions(+), 3 deletions(-)

diff --git a/System.v b/System.v
index 1872e51..4d0ddbb 100644
--- a/System.v
+++ b/System.v
@@ -55,6 +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,
@@ -64,14 +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]];
@@ -117,6 +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,
@@ -171,12 +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;
-- 
2.39.2