[Coco] Max baud rate for 68681 in MM/1?

[Dave Philipsen]

And any form of 68000 CPU should have no problem servicing interrupts at 
1Mbps.  The 68C681 has a receive buffer so you can receive many bytes 
while generating only one interrupt and even if it did generate an 
interrupt for every byte that's only 100k interrupts per second which I 
believe is quite doable with a 68000. Without looking at the technical 
info on the 6809 I would guess a 2 MHz 6809 could do it too although it 
might tax it a bit.

Dave


On 1/31/2016 9:16 PM, Dave Philipsen wrote:
> I have personally used a 68C681 UART in a 68HC11-based system that 
> transmits DMX512 theatrical standard lighting data at 250 kbps 
> (RS422/485).  It is tried and proven and currently running in about 
> 400 different locations in the US and a few other countries.  It is 
> using a 4 MHz clock as the BRG.
>
> Dave
>
>
> On 1/31/2016 3:33 PM, Joel Ewy wrote:
>> I read ambiguous information about the 68681 on the MM/1's I/O 
>> board.  Does anybody have a definitive word?  Page 2-5 of the MM/1 
>> technical manual claims that it can be run at "1 megabytes per 
>> second" (seriously 8M bits/sec?), but the table on page 9-2 and the 
>> text on 9-2 state that the maximum baud rate is 34,800.  Is this a 
>> pragmatic maximum based on the CPU's ability to service the DUART's 
>> on-chip buffers without interrupt-masking trickery, is it the real 
>> hard maximum for the 68681, or is it a hard maximum imposed by the 
>> MM/1's hardware? Anybody have any insight?
>>
>> JCE
>>
>>
>
>
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