[Coco] CoCo 128-column text mode

[Mark Schoenberger]

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  Old SAM modes work if CC Bit set. HR and CRES are Don't Care in SAM mode.
 Note the correspondence of HR2 HR0 to the text mode's bytes/line.
 Also that CRES bits shifted left one = number of colors. --Kev
 ----------------------------------------------------------------------------- FF9A  Border Palette Register RGBRGB (XX00 0000 = CoCo 1/2 compatible)
 FF9B  Reserved FF9C  Vertical Fine Scroll 
 FF9D  Screen Start Address Register 1 (bits 18-11)
 FF9E  Screen Start Address Register 0 (bits 10-3)
 FF9F  Horizontal Offset Register       
        Bit 7 = horizontal offset enable bit = 128 char width always 
        Bit 6 = X6  ... offset count (0-127)
        Bit 0 = X0 If Bit 7 set & in Text mode, then there are 128 chars (only 80 seen)/line.
 This allows an offset to be specified into a virtual 128 char/line screen, 
  useful for horizontal hardware scrolling on wide text or spreadsheets.


      From: Arthur Flexser <flexser at fiu.edu>
 To: CoCoList for Color Computer Enthusiasts <coco at maltedmedia.com> 
 Sent: Wednesday, January 7, 2015 11:32 AM
 Subject: Re: [Coco] CoCo 128-column text mode
   
So, you're saying the characters are seen as normal 80-column width ones,
but the cursor moves beyond the 80th character as the text scrolls leftward
so you can see the additional characters?

Don't recall ever hearing about this mode.  If I've described it correctly,
doesn't sound like a hardware mode at all, just something accomplished
through software.

Art

On Wed, Jan 7, 2015 at 11:27 AM, Allen Huffman <alsplace at pobox.com> wrote:

> Terry Trapp on the Facebook CoCo posted a link to a 1986 newsgroup posting
> by Kevin Darling which laid out what was known about the CoCo 3 hardware.
> One of the things noted in it was something I had completely forgotten
> about -- the 128-column hardware text mode.
>
> I had at least one RS-DOS word processor that used this, and the text
> would scroll at the end of the screen out to 128 characters. Once I moved
> to OS-9, I never used it again and just forgot about it.
>
> Was it ever used on anything else? I forgot what used it -- Simply Better,
> perhaps?
>
>                -- A
>
>
> --
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> Coco at maltedmedia.com
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>

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