Motorola 6847

According to the datasheets, there are non-interlaced (6847) and interlaced (6847Y) variants, plus the 6847T1 (non-interlaced only). The chips can be found with ceramic (L suffix), plastic (P suffix) or CERDIP (S suffix) packages. ==Die pictures==

File:MC6847 Metal Layer.jpg|MC6847 Die metal layer File:MC6847 Base Layer.jpg|MC6847 Die base layer ==Signal levels and color palette==

The chip outputs a NTSC-compatible progressive scan signal composed of one field of 262 lines 60 times per second. According to the MC6847 datasheet, colors are formed by the combination of three signals: Y luminance and \phi A and \phi B chroma, according to the YPbPr color space. These internal voltages are then converted into valid value ranges, generating signals that can drive a TV directly, or be used with a NTSC modulator (Motorola MC1372) for RF output. The resulting colors can be seen on the following image, illustrating the MC6847 standard character set and palette: The first eight colors were numbered 0 to 7 in the upper bits of the character set (when bit 7 was set, bits 4-6 represented the color number), but ColorBASIC's numbering was 1 higher than that in text mode, as it used 0 for black. At least on the Color Computer 1 and 2, the alternate palette of text modes (actually the text portion of semigraphic modes) was dark pink (or dark red) on light pink, of shades not listed here (and no dark orange), whereas the Color Computer 3, with a different chip, made it dark orange on orange. == Video modes ==

Possible MC6847 video display modes: ==Character generator==

The built-in character generator ROM offers 64 ASCII characters with 5x7 pixels. Characters can be green or orange, on dark green or orange background, with a possible "invert" attribute (dark character on a bright background). The internal character rom is organized as a matrix of 64x35 (2240 bits) where each column consists of the 35 bytes (5x7) needed to form a character. The character bits are stored sequentially in column order, that is 7 bits of column 0 followed by the 7 bits of column 1, and so on. 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 offered its customers the possibility of ordering the MC6847 with the internal ROM masked with a custom pattern. The customer would provide the ROM pattern on MCM2708 or MCM2716 PROMS or on a MDOS formatted 8-inch single sided, single density floppy disk. Motorola would then send 10 verification units for the customer to verify the ROM pattern. The MC6847 also supports an external character ROM. The Dragon 200-E, a spanish variant of the Dragon 64 is a great example of this. The machine had a daughterboard that fits on the MC6847 socket and had the VDG plus a 2532 EPROM and some decoding logic. The updated version of the chip (MC6847T1) had a 96 character ROM that included lowercase characters. Here you can see the default MC6847 and MC6847T1 default character sets, the Dragon 200-E one and the Dragon 200-E daughterboard. File:MC6847 Standard Charset.png|Standard character set File:MC6847T1 Standard Charset.png|MC6847T1 Standard character set File:MC6847 Dragon200E Charset.png|Dragon 200-E character set File:Dragon200E VDG Daughterboard.jpg|Dragon 200-E daughterboard ==See also==