[Coco] Drivewire question

[Steven Hirsch]

On Wed, 25 Mar 2009, Darren A wrote:

>> Granted, but I'm thinking of a case where you are reading from one
>> cartridge and writing to a device on the other.  From an electrical point
>> of view, you've just doubled the bandwidth demand.  Plus, there's
>> interrupt handling overhead and latency for the RS232 pack.  It will be
>> interesting to see if that combination can keep up with the bit-banger
>> port + cartridge port (which, indeed, is an expansion bus).
>>
>
> In the case of DriveWire, interrupts are not used for the serial data
> transfers. All transactions are initiated at the request of the CoCo
> and interrupts are masked during these transactions. Using the same
> tecnique for a 6551 version of DriveWire would not require any
> increase in bandwidth over the bus since the serial port  I/O is not
> interleaved with I/O to any other device during a transaction.

Yes, you are correct.  I've been spending too much time with modern 
multi-processor hardware, I think.  But, I'm still wondering if the 6551 
can be configured at 115.2K Baud given the crystal in the RS232 pack. 
Does anyone know the answer to this?



--