At 10:48 -0700 24-09-1997, Greg Troutman wrote:
>> That would allow 48/4=12 charachters per line (without flicker)!
>>
>> Can it be done?
>
>You mean a half-width font, instead of hard-coded graphics? Sure. Very
>problematic though. There is not enough time within the six-digit trick
>to read and combine the 4 bit parts into one graphics register. So, it
>has to be done in RAM beforehand, and that means 30 bytes for one 5
>scanline high line of text.
Yes, it's exactly what I was thinking.
>You can't very easily re-use that RAM area
>for drawing multiple lines of text in the same frame, because the loop
>that would combine 12 4-bit characters into 6 one byte graphics data,
>five scanlines high, would take well over a thousand cycles, I think,
>producing as many as 20 blank scanlines while you busily reload that RAM
>area...
Are you sure it would take so much time?
The font could be stored in this way...:
; letter "A"
byte %01000100
%10101010
%11101110
%10101010
%10101010
ie - the same 4-bit character twice in 1 byte, so that combining two of
them into 1 byte can be done without shifting bits...
P.
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