[Coco] CoCo 128-column text mode

[William Astle]

Theoretically, it would allow for 256 columns in a text mode with no 
attributes (1 byte per character). Bit 7 of FF9F actually forces the 
line width to 256 bytes instead of whatever the actual screen width is 
set to (each line starts 256 bytes past the previous one).

On 15-01-07 12:37 PM, Mark Schoenberger via Coco wrote:
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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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>
>>
>