[Coco] Drivewire question

[Roger Taylor]

At 07:19 PM 3/25/2009, you wrote:
>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?


The CoCo has been able to do 115200 bps with the 6551 since the 80's.


-- 
Roger Taylor

http://www.wordofthedayonline.com