[Open-graphics] Sample VGA translation code, for nanocontroller
wpmcnamara at yahoo.com
Wed Sep 5 21:43:02 EDT 2007
Jared Putnam wrote:
> VGA video memory is arranged into four 64k banks, called planes. When
> you read from video memory, (depending on the read mode) the card only
> gives you one value, it latches data on every active plane. There's a
> four-bit bitmask that determines this. When it writes memory, it
> writes from the latches to every active plane. Most modes just leave
> the latches on one setting; I think only Mode X lets you take advantage
> of this, though.
>> Is the 80x25 screen laid out as a linear array of 2000 16-bit words?
> Yes, but there is more than one screen, and you can switch between
Also, one of the memory banks (plane 2 IIRC) contains the font
definition for text modes.
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