Narrow RAM selection range

This commit is contained in:
Zane Kaminski 2023-04-08 04:11:03 -04:00
parent db5d8f86a6
commit a7a5da1763

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@ -28,18 +28,70 @@ module CS(
assign RAMCS = RAMCS0X && !Overlay;
wire VidRAMCSWR64k = RAMCS && !nWE && (A[23:20]==4'h3) && (A[19:16]==4'hF); // 3F0000-3FFFFF
wire VidRAMCSWR = VidRAMCSWR64k && (
(A[15:12]==4'h2) || // 1792 bytes RAM, 2304 bytes video
(A[15:12]==4'h2 && // 1792 bytes RAM, 2304 bytes video
(A[11:8]==4'h7 ||
A[11:8]==4'h8 ||
A[11:8]==4'h9 ||
A[11:8]==4'hA ||
A[11:8]==4'hB ||
A[11:8]==4'hC ||
A[11:8]==4'hD ||
A[11:8]==4'hE ||
A[11:8]==4'hF)) ||
(A[15:12]==4'h3) || // 4096 bytes video
(A[15:12]==4'h4) || // 4096 bytes video
(A[15:12]==4'h5) || // 4096 bytes video
(A[15:12]==4'h6) || // 4096 bytes video
(A[15:12]==4'h7) || // 3200 bytes video, 896 bytes RAM,
(A[15:12]==4'hA) || // 256 bytes RAM, 768 bytes sound, 768 bytes RAM, 2304 bytes video
(A[15:12]==4'h7 && // 3200 bytes video, 896 bytes RAM
(A[11:8]==4'h0 ||
A[11:8]==4'h1 ||
A[11:8]==4'h2 ||
A[11:8]==4'h3 ||
A[11:8]==4'h4 ||
A[11:8]==4'h5 ||
A[11:8]==4'h6 ||
A[11:8]==4'h7 ||
A[11:8]==4'h8 ||
A[11:8]==4'h9 ||
A[11:8]==4'hA ||
A[11:8]==4'hB ||
(A[11:8]==4'hC && !A[7]))) ||
(A[15:12]==4'hA && // 256 bytes RAM, 768 bytes sound, 768 bytes RAM, 2304 bytes video
(A[11:8]==4'h1 ||
A[11:8]==4'h2 ||
A[11:8]==4'h3 ||
A[11:8]==4'h7 ||
A[11:8]==4'h8 ||
A[11:8]==4'h9 ||
A[11:8]==4'hA ||
A[11:8]==4'hB ||
A[11:8]==4'hC ||
A[11:8]==4'hD ||
A[11:8]==4'hE ||
A[11:8]==4'hF)) ||
(A[15:12]==4'hB) || // 4096 bytes video
(A[15:12]==4'hC) || // 4096 bytes video
(A[15:12]==4'hD) || // 4096 bytes video
(A[15:12]==4'hE) || // 4096 bytes video
(A[15:12]==4'hF)); // 3200 bytes video, 128 bytes RAM (system error space), 768 bytes sound
(A[15:12]==4'hF && // 3200 bytes video, 128 bytes RAM (system error space), 768 bytes sound
(A[11:8]==4'h0 ||
A[11:8]==4'h1 ||
A[11:8]==4'h2 ||
A[11:8]==4'h3 ||
A[11:8]==4'h4 ||
A[11:8]==4'h5 ||
A[11:8]==4'h6 ||
A[11:8]==4'h7 ||
A[11:8]==4'h8 ||
A[11:8]==4'h9 ||
A[11:8]==4'hA ||
A[11:8]==4'hB ||
(A[11:8]==4'hC && !A[7]) ||
A[11:8]==4'hD ||
A[11:8]==4'hE ||
A[11:8]==4'hF));
assign SndRAMCSWR = VidRAMCSWR64k && (
((A[15:12]==4'hF) && ((A[11:8]==4'hD) || (A[11:8]==4'hE) || (A[11:8]==4'hF))) ||
((A[15:12]==4'hA) && ((A[11:8]==4'h1) || (A[11:8]==4'h2) || (A[11:8]==4'h3))));
/* Select signals - IOB domain */
assign IACS = (A[23:20]==4'hF) && (A[19:18]==2'b11); // IACK
@ -54,7 +106,7 @@ module CS(
(A[23:20]==4'h7) || // empty
(A[23:20]==4'h6) || // empty
(A[23:20]==4'h5) || // SCSI
((A[23:20]==4'h4) && Overlay) ||
VidRAMCSWR; // ROM once
((A[23:20]==4'h4) && Overlay) || // ROM once
VidRAMCSWR; // Write to video RAM
assign IOPWCS = VidRAMCSWR;
endmodule