Motorola 6847

The MC6847 is a Video Display Generator (VDG) first introduced by Motorola in 1978^[3] and used in the TRS-80 Color Computer,^[4] Dragon 32/64,^[5] Laser 200,^[6] TRS-80 MC-10/Matra Alice,^[7] NEC PC-6000 series,^[8] Acorn Atom,^[9] Gakken Compact Vision TV Boy^[10] and the APF Imagination Machine,^[11] among others. It is a relatively simple display generator intended for NTSC television output: capable of displaying alphanumeric text, semigraphics,^[12] and raster graphics contained within a roughly square display matrix 256 pixels wide by 192 lines high.

The ROM includes a 5 x 7 pixel font, compatible with 6-bit ASCII. Effects such as inverse video or colored text (green on dark green; orange on dark orange) are possible.^[13]

The hardware palette is composed of twelve colors: black, green, yellow, blue, red, buff (almost-but-not-quite white), cyan, magenta, and orange (two extra colors, dark green and dark orange, are the ink colours for all alphanumeric text mode characters, and a light orange color is available as an alternative to green as the background color).^[14] According to the MC6847 datasheet, the colors are formed by the combination of three signals: ${\displaystyle Y}$ with 6 possible levels, ${\displaystyle R-Y}$ (or ${\displaystyle \phi A}$ with 3 possible levels) and ${\displaystyle B-Y}$ (or ${\displaystyle \phi B}$ with 3 possible levels), based on the YPbPr colorspace, and then converted for output into a NTSC analog signal.^[13]

The low display resolution is a necessity of using television sets as display monitors. Making the display wider risked cutting off characters due to overscan. Compressing more dots into the display window would easily exceed the resolution of the television and be useless.^[15][16]