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81 lines
1.8 KiB
Plaintext
81 lines
1.8 KiB
Plaintext
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// SL 2019-10
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//
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// GNU AFFERO GENERAL PUBLIC LICENSE
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// Version 3, 19 November 2007
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//
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// A copy of the license full text is included in
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// the distribution, please refer to it for details.
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algorithm ntsc(
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output! uint1 ntsc_hs,
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output! uint1 ntsc_vs,
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output! uint1 active,
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output! uint1 vblank,
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output! uint10 ntsc_x,
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output! uint10 ntsc_y
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) <autorun> {
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uint10 H_FRT_PORCH = 7;
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uint10 H_SYNCH = 23;
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uint10 H_BCK_PORCH = 23;
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uint10 H_RES = 256;
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uint10 V_FRT_PORCH = 5;
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uint10 V_SYNCH = 3;
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uint10 V_BCK_PORCH = 14;
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uint10 V_RES = 240;
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uint10 HS_START = 0;
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uint10 HS_END = 0;
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uint10 HA_START = 0;
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uint10 H_END = 0;
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uint10 VS_START = 0;
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uint10 VS_END = 0;
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uint10 VA_START = 0;
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uint10 V_END = 0;
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uint10 xcount = 0;
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uint10 ycount = 0;
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HS_START := H_FRT_PORCH;
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HS_END := H_FRT_PORCH + H_SYNCH;
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HA_START := H_FRT_PORCH + H_SYNCH + H_BCK_PORCH;
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H_END := H_FRT_PORCH + H_SYNCH + H_BCK_PORCH + H_RES;
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VS_START := V_FRT_PORCH;
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VS_END := V_FRT_PORCH + V_SYNCH;
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VA_START := V_FRT_PORCH + V_SYNCH + V_BCK_PORCH;
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V_END := V_FRT_PORCH + V_SYNCH + V_BCK_PORCH + V_RES;
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ntsc_hs := ((xcount >= HS_START && xcount < HS_END));
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ntsc_vs := ((ycount >= VS_START && ycount < VS_END));
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active := (xcount >= HA_START && xcount < H_END)
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&& (ycount >= VA_START && ycount < V_END);
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vblank := (ycount < VA_START);
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xcount = 0;
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ycount = 0;
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while (1) {
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ntsc_x = (active) ? xcount - HA_START : 0;
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ntsc_y = (vblank) ? 0 : ycount - VA_START;
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if (xcount == H_END-1) {
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xcount = 0;
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if (ycount == V_END-1) {
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ycount = 0;
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} else {
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ycount = ycount + 1;
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}
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} else {
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xcount = xcount + 1;
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}
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}
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}
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// -------------------------
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