Fixed

cpld/RAM.v

@@ -1,6 +1,7 @@
 module RAM(
 	/* MC68HC000 interface */
-	input CLK, input [21:1] A, input nWE, input nAS, input nLDS, input nUDS,
+	input CLK, input [21:1] A, input nWE,
+	input nAS, input nLDS, input nUDS, input nDTACK,
 	/* AS cycle detection */
 	input BACT, 
 	/* Select and ready signals */
@@ -9,13 +10,16 @@ module RAM(
 	input RefReqIn, input RefUrgIn,
 	/* DRAM and NOR flash interface */
 	output [11:0] RA, output nRAS, output reg nCAS,
-	output nLWE, output nUWE, output nOE, output nROMCS, output nROMWE);
-	
+	output nLWE, output nUWE, output reg nOE, output nROMCS, output nROMWE);
+
+	/* BACT and /DTACK registration */
+	reg BACTr; always @(posedge CLK) BACTr <= BACT;
+	reg DTACKr; always @(posedge CLK) DTACKr <= !nDTACK;
+
 	/* RAM control state */
-	reg [3:0] RS = 0;
+	reg [2:0] RS = 0;
 	reg RASEN = 0;
 	reg RASEL = 0;
-	reg CAS = 0;
 	reg RASrr = 0;
 	reg RASrf = 0;
 
@@ -23,20 +27,22 @@ module RAM(
 	reg RefDone; // Refresh done "remember"
 	always @(posedge CLK) begin
 		if (!RefReqIn && !RefUrgIn) RefDone <= 0;
-		else if (RS[3]) RefDone <= 1;
+		else if (RS[2]) RefDone <= 1;
 	end
 	wire RefReq = RefReqIn && !RefDone;
 	wire RefUrg = RefUrgIn && !RefDone;
 
 	/* RAM control signals */
-	assign nRAS =   !((!nAS && RAMCS && RASEN) || RASrr || RASrf);
-	assign nOE =    !(!nAS &&  nWE); // Shared with ROM
-	assign nLWE =   !(!nLDS && !nWE && RASEL);
-	assign nUWE =   !(!nUDS && !nWE && RASEL);
+	assign nRAS = !((!nAS && RAMCS && RASEN) || RASrr || RASrf);
+	assign nLWE = !(!nLDS && !nWE && RASEL);
+	assign nUWE = !(!nUDS && !nWE && RASEL);
 
 	/* ROM control signals */
 	assign nROMCS = !ROMCS;
-	assign nROMWE = !((!nAS && !nWE));
+	assign nROMWE = !(!nAS && !nWE);
+
+	/* Shared ROM and RAM /OE control */
+	always @(posedge CLK) nOE <= !(BACT && !nWE && !(BACTr && DTACKr));
 
 	/* RAM address mux (and ROM address on RA8) */
 	// RA11 doesn't do anything so both should be identical.
@@ -54,120 +60,115 @@ module RAM(
 	assign RA[04] = !RASEL ? A[11] : A[03];
 	assign RA[01] = !RASEL ? A[10] : A[02];
 	assign RA[00] = !RASEL ? A[09] : A[01];
-	
-	reg BACTr; always @(posedge CLK) BACTr <= BACT;
+
+	wire RS0toRef = (RefReq &&  BACT && !BACTr && !RAMCS0X) ||
+					(RefUrg && !RASEN) ||
+					(RefUrg &&  BACT && !RAMCS0X) ||
+					(RefUrg && !BACT);
 	
 	always @(posedge CLK) begin
-		case (RS[3:0])
-			0: begin
-				if (( BACT && !BACTr && !RAMCS0X && RefReq) ||
-					 (!BACT && RefUrg) ||
-					 ( BACT && RefUrg && !RAMCS0X) ||
-					 (!RASEN)) begin
-					RS <= 8;
+		case (RS[2:0])
+			0: begin // Idle/ready
+				if (RS0toRef) begin // Go to refresh
+					RS <= 4;
 					RASEL <= 0;
-					CAS <= 1;
 					RASrr <= 0;
 					RASEN <= 0;
 					RAMReady <= 0;
-				end else if (BACT && RAMCS && RASEN) begin
+				end else if (BACT && RAMCS && RASEN) begin // Access RAM
 					RS <= 1;
 					RASEL <= 1;
-					CAS <= 1;
 					RASrr <= 1;
 					RASEN <= 1;
 					RAMReady <= 1;
-				end else begin
+				end else begin // Stay in idle/ready
 					RS <= 0;
 					RASEL <= 0;
-					CAS <= 0;
 					RASrr <= 0;
 					RASEN <= 1;
 					RAMReady <= 1;
 				end
-			end 1: begin
+			end 1: begin // RAM access
 				RS <= 2;
 				RASEL <= 1;
-				CAS <= 1;
 				RASrr <= 0;
 				RASEN <= 0;
 				RAMReady <= 1;
-			end 2: begin
-				RS <= 3;
-				RASEL <= 0;
-				CAS <= 0;
-				RASrr <= 0;
-				RASEN <= 0;
-				RAMReady <= 1;
-			end 3: begin
-				if (BACT) begin
+			end 2: begin // finish RAM access
+				if (DTACKr) begin // Cycle ending
 					RS <= 3;
 					RASEL <= 0;
-					CAS <= 0;
 					RASrr <= 0;
 					RASEN <= 0;
 					RAMReady <= 1;
-				end else if (RefUrg) begin
-					RS <= 8;
+				end else begin
+					RS <= 2;
+					RASEL <= 1;
+					RASrr <= 0;
+					RASEN <= 0;
+					RAMReady <= 1;
+				end
+			end 3: begin  //AS cycle complete
+				if (RefUrg)  begin // Refresh RAS
+					RS <= 4;
+					RASEL <= 0;
+					RASrr <= 1;
+					RASEN <= 0;
+					RAMReady <= 0;
+				end else begin // Cycle ended so go abck to idle/ready
+					RS <= 0;
+					RASEL <= 0;
+					RASrr <= 0;
+					RASEN <= 1;
+					RAMReady <= 1;
+				end
+			end 4: begin // Refresh RAS I
+				RS <= 5;
+				RASEL <= 0;
+				RASrr <= 1;
+				RASEN <= 0;
+				RAMReady <= 0;
+			end 5: begin // Refresh RAS II
+				RS <= 6;
+				RASEL <= 0;
+				RASrr <= 1;
+				RASEN <= 0;
+				RAMReady <= 0;
+			end 6: begin // Refresh precharge I / II
+				if (RASrr) begin
+					RS <= 6;
 					RASEL <= 0;
-					CAS <= 1;
 					RASrr <= 0;
 					RASEN <= 0;
 					RAMReady <= 0;
 				end else begin
-					RS <= 0;
+					RS <= 7;
 					RASEL <= 0;
-					CAS <= 0;
 					RASrr <= 0;
-					RASEN <= 1;
-					RAMReady <= 1;
+					RASEN <= 0;
+					RAMReady <= 0;
 				end
-			end 8: begin
-				RS <= 9;
-				RASEL <= 0;
-				CAS <= 1;
-				RASrr <= 1;
-				RASEN <= 0;
-				RAMReady <= 0;
-			end 9: begin
-				RS <= 10;
-				RASEL <= 0;
-				CAS <= 0;
-				RASrr <= 1;
-				RASEN <= 0;
-				RAMReady <= 0;
-			end 10: begin
-				RS <= 11;
-				RASEL <= 0;
-				CAS <= 0;
-				RASrr <= 0;
-				RASEN <= 0;
-				RAMReady <= 0;
-			end 11: begin
-				RS <= 15;
-				RASEL <= 0;
-				CAS <= 0;
-				RASrr <= 0;
-				RASEN <= 0;
-				RAMReady <= 0;
-			end 15: begin
+			end 7: begin // Reenable RAM and go to idle/ready
 				RS <= 0;
 				RASEL <= 0;
-				CAS <= 0;
-				RASrr <= 0;
-				RASEN <= 1;
-				RAMReady <= 1;
-			end default: begin
-				RS <= 0;
-				RASEL <= 0;
-				CAS <= 0;
 				RASrr <= 0;
 				RASEN <= 1;
 				RAMReady <= 1;
 			end
 		endcase
 	end
-	always @(negedge CLK) RASrf <= RS==1;
-	always @(negedge CLK) nCAS <= !CAS;
+	always @(negedge CLK) begin
+		RASrf <= RS==1;
+		case (RS[2:0])
+			0: nCAS <= !RS0toRef;
+			1: nCAS <= 0;
+			2: nCAS <= DTACKr;
+			3: nCAS <= !RefUrg;
+			4: nCAS <= !RefUrg;
+			5: nCAS <= 1;
+			6: nCAS <= 1;
+			7: nCAS <= 1;
+		endcase
+	end
 
 endmodule

cpld/WarpSE.v

@@ -71,7 +71,8 @@ module WarpSE(
 	wire RAMReady;
 	RAM ram(
 		/* MC68HC000 interface */
-		FCLK, A_FSB[21:1], nWE_FSB, nAS_FSB, nLDS_FSB, nUDS_FSB,
+		FCLK, A_FSB[21:1], nWE_FSB,
+		nAS_FSB, nLDS_FSB, nUDS_FSB, nDTACK_FSB,
 		/* AS cycle detection */
 		BACT,
 		/* Select and ready signals */