Re: Create Text & High Resolution into Screen

["Bill Garber" <willy46pa@comcast.net>]

"Eric Smith" <eric-no-spam-for-me@brouhaha.com> wrote in message
qhy8wq5zj0.fsf@ruckus.brouhaha.com">news:qhy8wq5zj0.fsf@ruckus.brouhaha.com...
> <BPARKOFF4@satx.rr.com> writes:
> >     I understand that every 6502's half cycle reads $400-$7FF for Text
Mode
> > and $2000-$3FFF for HGR Mode before second half cycle paints 14 pixels
to
> > the screen.  I think that Text Mode has to paint 56 pixels (7x8) to the
> > screen each Text character during every second half cycle, but only 14
> > pixels will be painted for HGR Mode.
>
> No.  In text mode, during each video cycle, one character is fetched from
> RAM, and the character code and the scan line within the character (zero
> for the top line through seven for the bottom line) are used as inputs to
> the character generator (2513 in early models, a normal 2K*8 ROM in
> rev 7 and later).

I must differ with you here in that more than one character can
be fetched from RAM. Entire lines can be fetched and displayed.
Also, I can not buy anything being an "input" to a ROM ( Read
Only Memory ).

Bill @ GarberStreet Enterprizez };-)
Web Site - http://garberstreet.netfirms.com
Email - willy46pa@comcast.net

> Each line of text takes 8 scan lines of 65 clocks each (520 total).  On
> each scan line, 40 of the RAM cycles are used to read the actual text.
> The remaining RAM cycles (25 per scan line) fetch data that is not
> displayed, and serve only to perform RAM refresh.



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