[Coco] Interbank Incident for Drivewire ?

[Aaron Wolfe]

On Tue, Nov 27, 2012 at 5:13 PM, Robert Gault <robert.gault at att.net> wrote:
> Arthur Flexser wrote:
>>
>> Out of curiosity, why would it work with a CoCo 2 but not a CoCo 1?
>>
>> Art
>>
>
> Actually I don't know what will happen and made an assumption based on the
> NitrOS-9 project. If you look at the Level1/coco section, you will see that
> two types of disks get built, coco1_dw3.dsk and coco2_dw3.dsk. There is no
> such distinction for non-Drivewire disks.
>
> Aaron, Boisy, or Darren Atkinson would be the ones to ask about this
> difference, and what it is.
>

I believe this is because CoCo 1's need to run the bitbanger at only
38,400 bps due to instability, whereas the CoCo 2 can operate reliably
at 57,600.  The timing in the bitbanger output is determined by the
instructions in the driver, so its a different module.

> =====
>
>  There are some other things unusual about Drivewire. It makes use of $FF41
> and $FF42 as I/O ports and the DAC at $FF20. The first two do not correspond
> to any I/O ports I can find info about.

This is the "Becker/Boisy" interface used by the Coco3FPGA and
emulators.  It is a simple FIFO designed for situations where you have
external I/O processing capability (and it allows very high speeds
beyond anything the bitbanger can do).  Unless you load the dw3_becker
low level module (which cannot be used at the same time as the regular
bitbanger module) then there should be nothing accessing those
addresses AFAIK.

>  Interbank can use the Speech Sound PAK to talk and play music. This PAK is
> addressed at $FF7D and $FF7E. Interbank does not use the DAC for sound. When
> the game is played via Drivewire and you indicate an SSP is present, you can
> hear music and speech but there is a constant very loud static background
> noise.
>  Unless there is ghosting between the I/O ports $FF41,$FF42 and $FF7D,
> $FF7E, or NitrOS-9 Level1 is not compatible with the SSP, there is no
> logical source for this noise.
>
>
> Robert
>
>
>
>
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