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.

The ROM includes a 5 x 7 pixel font, compatible with 6-bit ASCII.

[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).

with 3 possible levels), based on the YPbPr colorspace, and then converted for output into a NTSC analog signal.

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.

The chip outputs a NTSC-compatible progressive scan signal composed of one field of 262 lines 60 times per second.

[17][18] These signals can drive a TV directly, or be used with a NTSC modulator (Motorola MC1372) for RF output.

[17][18] The following table shows the signal values used:[17][18] Notes: 1) The colors shown are adjusted for maximum brightness and only approximate (different color spaces are used on TV - BT601 and web pages - sRGB).

Characters can be green or orange, on dark green or orange background, with a possible "invert" attribute (dark character on a bright background).

The following picture shows the bits overlapped on top of the rom array, with the ones of the first character (@) in different colours to highlight the organization.

Motorola would then send 10 verification units for the customer to verify the ROM pattern.

The machine had a daughterboard that fits on the MC6847 socket and had the VDG plus a 2532 EPROM and some decoding logic.