The service manual covers the hardware side fairly well, but I'm not aware of 
the actual communication protocol being available anywhere.

As Willard says, the DOS and disk BASIC have to be loaded from disk; the SCREEN 
command only selects the display mode.

m

----- Original Message ----- 
From: "Willard Goosey" <goo...@sdc.org>
To: <m100@lists.bitchin100.com>
Cc: <m...@bitchin100.com>
Sent: Saturday, August 05, 2017 2:01 AM
Subject: Re: [M100] DVI


> On Fri, 4 Aug 2017 18:17:17 +0000 (UTC)
> Jan Vanden Bossche <jan80...@yahoo.com> wrote:
> 
> 
>>Is there somewhere a description of how the DVI interface
>> works, and what signals (type & speed) come out (and where) of the
>> Model T ? And how they have to be interpreted ?Did you need to load
>> any software on the T to make it work, or was a simple screen 1,0
>> enough ? Is there a general description of the workings of a DVI,
>> somewhere ?
>>
> I don't know the gruesome details, but the DVI connects via the
> expansion bus, and there is a RAM-resident "dos" that has to be
> loaded from somewhere to actually use the DVI.
> 
> I know the DVI is a z80 box with, IIRC, a 1793 or 1797 FDC, and
> (probably) a 6845 (or clone) video driver. It wasn't developed at Tandy
> so is probably not just a Model 1 with a weird ROM. It writes disks
> that can be read by other retro machines, and the filesystem is
> *almost* the same as CoCo Disk BASIC (Microsoft FAT8). At one point I
> had my CoCo reading DVI disks (that were created by teledisk) but that
> was a long time ago.
> 
> And that, I'm afraid, is everything I know about the DVI. ;-(
> 
> Willard
> -- 
> Willard Goosey  goo...@sdc.org
> Socorro, New Mexico, USA
> I search my heart and find Cimmeria, land of Darkness and the Night.
>  -- R.E. Howard

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