[Coco] GIME text modes and font data

[John Kent]

On 3/09/2012 7:12 PM, William Astle wrote:
> To answer a couple of questions in there:
>
> The character width is 8 pixels. The HPRINT font uses 8 rows per 
> character but the GIME can do up to 12 rows per character. I assume 
> rows 9-12 are blanks.
>
> As far as what mess is doing: it appears to be using the HPRINT font 
> data in the ROM as the bitmap data for the hardware font. I know it is 
> doing that because I had mess use a different ROM (which it complained 
> about but let me proceed) which had various patterns in the various 
> relevant address ranges and those patterns showed up on screen in the 
> text modes instead of proper characters. Given that your assessment 
> agrees with mine (from first principles), I assume mess is cheating 
> since I don't see how the real hardware could be doing what mess is 
> doing.
>

I don't know what HPRINT is exactly, so I can't really comment on it's use.
I'd have to look at the graphics modes for the 6847 again.
I was working on my own version of the 6847 at one stage but that was a 
while ago.
I think there was a mode where the graphics pixels are arrange in a line 
horizontally.
It's possible that the character font is used in conjunction with one of 
the graphics modes so that you can display characters mixed with graphics.
Maybe that is what you mean by HPRINT.
Is it a BASIC command for printing characters in graphics mode ?

It is most likely that the rows 9-12 are blank, although 12 scan lines 
can be divided up into 3 groups of 4 scan lines or 2 groups of 6 scan 
lines for the various graphics modes.
12 can be divided up in a number of different ways, so even though not 
all the scan lines might not be used in text mode they can be used in 
graphics mode.

John.

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