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Fix some RAM issues (is RAMEN fix really necessary?)

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This commit is contained in:
Zane Kaminski 2024-10-06 23:07:15 -04:00
parent b847e10b1a
commit 8e40091786
1 changed files with 13 additions and 5 deletions
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18
cpld/RAM.v
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@ -7,7 +7,7 @@ module RAM(
/* Select and ready signals */
input RAMCS, input RAMCS0X, input ROMCS, input ROMCS4X,
/* RAM ready output */
output RAMReady,
output reg RAMReady,
/* Refresh Counter Interface */
input RefReqIn, input RefUrgIn,
/* DRAM and NOR flash interface */
@ -21,19 +21,18 @@ module RAM(
reg RASrf;
reg RefCAS;
reg CASEndEN;
assign RAMReady = RASEN;
/* Refresh command generation */
reg RefDone; // Refresh done "remember"
always @(posedge CLK) begin
if (!RefReqIn) RefDone <= 0;
if (!RefReqIn && !RefUrgIn) RefDone <= 0;
else if (RS[2]) RefDone <= 1;
end
wire RefReq = RefReqIn && !RefDone;
wire RefUrg = RefUrgIn && !RefDone;
/* RAM control signals */
assign nRAS = !((!nAS && RAMCS0X && RASEN) || RASrf);
assign nRAS = !((!nAS && RAMCS && RASEN) || RASrf);
assign nOE = 0;//!( !nAS && RAMCS && BACTr);
assign nLWE = !(!nLDS && RASEL && !nWE);
assign nUWE = !(!nUDS && RASEL && !nWE);
@ -65,7 +64,7 @@ module RAM(
(RefUrg && !BACT) ||
// Urgent refresh during non-RAM access
(RefUrg && BACT && !RAMCS0X);
wire RS0toRAM = BACT && RAMCS0X && RASEN;
wire RS0toRAM = BACT && RAMCS && RASEN;
always @(posedge CLK) begin
case (RS[2:0])
@ -76,26 +75,31 @@ module RAM(
RASEL <= BACT && RAMCS;
RefCAS <= RS0toRef;
RASEN <= !RS0toRef;
RAMReady <= !RS0toRef;
end 1: begin // RAM access
if (!nDTACK || !BACT) RS <= 2; // Cycle ending
else RS <= 1; // Cycle not ending yet
RASEL <= 1;
RefCAS <= 0;
RASEN <= nDTACK;
RAMReady <= 1;
end 2: begin // finish RAM access
RS <= 3;
RASEL <= 0;
RefCAS <= 0;
RASEN <= 0;
RAMReady <= 1;
end 3: begin //AS cycle complete
if (RefUrg) begin // Refresh RAS
RS <= 4;
RefCAS <= 1;
RASEN <= 0;
RAMReady <= 0;
end else begin // Cycle ended so go back to idle/ready
RS <= 0;
RefCAS <= 0;
RASEN <= 1;
RAMReady <= 1;
end
RASEL <= 0;
end 4: begin // Refresh RAS I
@ -103,21 +107,25 @@ module RAM(
RASEL <= 0;
RefCAS <= 0;
RASEN <= 0;
RAMReady <= 0;
end 5: begin // Refresh RAS II
RS <= 6;
RASEL <= 0;
RefCAS <= 0;
RASEN <= 0;
RAMReady <= 0;
end 6: begin // Refresh precharge I
RS <= 7;
RASEL <= 0;
RefCAS <= 0;
RASEN <= 0;
RAMReady <= 0;
end 7: begin // Reenable RAM and go to idle/ready
RS <= 0;
RASEL <= 0;
RefCAS <= 0;
RASEN <= 1;
RAMReady <= 1;
end
endcase
end