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SE-VGA
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Fixed image overwrite issues

This commit is contained in:
techav 2021-10-12 23:28:59 -05:00
parent 5377d05895
commit 4be7d63105
1 changed files with 13 additions and 8 deletions
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21
se-xga.sv
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@ -52,7 +52,8 @@ end
// horizontal and vertical sync signals
always_comb begin
if(hCount >= 11'd1048 && hCount < 11'd1184) nhSyncInner <= 0;
//if(hCount >= 11'd1048 && hCount < 11'd1184) nhSyncInner <= 0;
if(hCount >= 11'd1052 && hCount < 11'd1187) nhSyncInner <= 0;
else nhSyncInner <= 1;
nhSync <= nhSyncInner;
@ -72,7 +73,7 @@ wire hLoad; // load pixel data from vram when asserted
assign vidActive = hActive & vActive;
always_comb begin
if(hCount >= 0 && hCount < 1024) hActive <= 1;
if(hCount >= 3 && hCount < 1027) hActive <= 1;
else hActive <= 0;
if(vCount >= 0 && vCount < 684) vActive <= 1;
@ -181,12 +182,12 @@ always_comb begin
end
S3, S4: begin
// address bus for upper write cycles
vramAddr[14:1] <= cpuAddr[14:1] - 14'h1380;
vramAddr[14:1] <= cpuAddrShift;
vramAddr[0] <= 0;
end
S5, S6: begin
// address bus for lower write cycles
vramAddr[14:1] <= cpuAddr[14:1] - 14'h1380;
vramAddr[14:1] <= cpuAddrShift;
vramAddr[0] <= 1;
end
default: begin
@ -210,8 +211,6 @@ end
* signals and see the strapped pattern output on screen.
*****************************************************************************/
logic [8:0] vidData; // the video data we are displaying
//wire [2:0] vidSeq; // sequence counter, derived from hCount
//wire tick, tock; // even/odd pulses of pixel clock divided by 2
// output shift register
always @(posedge pixClk) begin
@ -221,7 +220,7 @@ always @(posedge pixClk) begin
end else if(!hCount[0] && vidActive) begin
// shift out video data
vidData[8:1] <= vidData[7:0];
vidData[0] <= 0;
vidData[0] <= 1;
end
end
@ -263,9 +262,15 @@ reg cpuUWriteSrv, cpuLWriteSrv, cpuVIASrv;
wire cpuBufSel;
wire cpuBufAddr;
reg vidBufSel;
wire [13:0] cpuAddrShift = cpuAddr[14:1] - 14'h1380;
wire cpuBufRange;
// these are some helpful signals that shortcut the CPU buffer & VIA addresses
always_comb begin
/*if(cpuAddr[14:1] >= 14'h1380
&& cpuAddr[14:1] < 14'h3E40) cpuBufRange <= 1;
else cpuBufRange <= 0;*/
cpuBufRange <= (cpuAddr[14:1] >= 14'h1380) & (cpuAddr[14:1] < 14'h3E40);
if(!ncpuAS && !cpuRnW
&& !cpuAddr[23] && !cpuAddr[22] // first two bits always 0
&& !(cpuAddr[21] ^ ramSize[2]) // compare with RAM Size bits
@ -273,7 +278,7 @@ always_comb begin
&& !(cpuAddr[19] ^ ramSize[0])
&& cpuAddr[18] && cpuAddr[17] // next three bits always 1
&& cpuAddr[16] // skip 15, it selects buffers
&& (cpuAddr[14] || cpuAddr[13]) // if neither 13|14 then not buffer
&& cpuBufRange // only select buffer addresses
) begin
cpuBufAddr <= 1;
end else begin