Index: src/mess/video/m6847.c
===================================================================
--- src/mess/video/m6847.c (revision 9454)
+++ src/mess/video/m6847.c (working copy)
@@ -966,6 +966,60 @@
#define ATTOTIME_STRING_PRECISION 9
+/* MC6847 video output pins: Y, phiA, phiB (Y'UV color space).
+ *
+ * Y voltage levels:
+ * VB ("Black") = 0.72V; VWL ("White Low") = 0.65V; VWM ("White Medium") = 0.54V;
+ * VWH ("White High") = 0.42V.
+ *
+ * phiA and phiB voltage levels:
+ * VOL ("Output Low") = 1.0V; VR ("Reference"?) = 1.5V; VIH ("Input High") = 2.0V.
+ *
+ * Color composition:
+ *
+ * COLOR | Y | phiA | phiB
+ * ------------+-----+------+------
+ * GREEN | VWM | VOL | VOL
+ * YELLOW | VWH | VOL | VR
+ * BLUE | VWL | VIH | VR
+ * RED | VWL | VR | VIH
+ * WHITE | VWH | VR | VR
+ * CYAN | VWM | VR | VOL
+ * MAGENTA | VWM | VIH | VIH
+ * ORANGE | VWM | VOL | VIH
+ * BLACK | VB | VR | VR
+ * DARK GREEN | VB | VOL | VOL
+ * DARK ORANGE | VB | VOL | VIH
+ *
+ *
+ * Mapping voltages to a 0~255 range:
+ *
+ * Y values:
+ * VB = 0; VWL = 59; VWM = 153; VWH = 255.
+ *
+ * phiA and phiB values:
+ * VOL = -128; VR = 0; VIH = +128.
+ *
+ *
+ * Y'UV to RGB convertion:
+ * R = Y' + 1.13983 x U
+ * G = Y' - 0.39465 x U - 0.58060 x V
+ * B = Y' + 2.03211 x V
+ *
+ * So we get:
+ * GREEN = Y'UV(153,-128,-128) = RGB(7,277,-107) --> #07ff00
+ * YELLOW = Y'UV(255,-128,0) = RGB(255,305,-5) --> #ffff00
+ * BLUE = Y'UV(59,+128,0) = RGB(59,8,319) --> #3b08ff
+ * RED: Y'UV(59,0,+128) = RGB(204,-15,59) --> #cc003b
+ * WHITE: Y'UV(255,0,0) = RGB(255,255,255) --> #ffffff
+ * CYAN: Y'UV(153,0,-128) = RGB(7,227,153) --> #07e399
+ * MAGENTA: Y'UV(153,+128,+128) = RGB(298,28,413) --> #ff1cff
+ * ORANGE: Y'UV(153,-128,+128) = RGB(298,129,-107) --> #ff8100
+ * BLACK: Y'UV(0,0,0) = RGB(0,0,0) --> #000000
+ * DARK GREEN: Y'UV(0,-128,-128) = RGB(-145,124,-260) --> #007c00
+ * DARK ORANGE: Y'UV(0,-128,+128) = RGB(145,-23,-260) --> #910000
+ */
+
#define M6847_RGB(r,g,b) ((r << 16) | (g << 8) | (b << 0))
@@ -980,9 +1034,9 @@
M6847_RGB(0xff, 0x1c, 0xff), /* MAGENTA */
M6847_RGB(0xff, 0x81, 0x00), /* ORANGE */
+ M6847_RGB(0x00, 0x7c, 0x00), /* DARK GREEN */
+ M6847_RGB(0x07, 0xff, 0x00), /* GREEN */
M6847_RGB(0x00, 0x00, 0x00), /* BLACK */
- M6847_RGB(0x00, 0x7c, 0x00), /* GREEN */
- M6847_RGB(0x00, 0x00, 0x00), /* BLACK */
M6847_RGB(0xff, 0xff, 0xff), /* BUFF */
M6847_RGB(0x00, 0x7c, 0x00), /* ALPHANUMERIC DARK GREEN */
