68661 EPCI woes. Can anyone help?

Chuck Guzis cclist at sydex.com
Mon Aug 13 14:33:07 CDT 2007


On 13 Aug 2007 at 8:10, dwight elvey wrote:

> For async you should be using
> X16 and the correct divide settings for x16. 1X is only for sync com.
> You need to compensate the divide when doing X16. It is different
> than 1X.

On the 2661/68661, if the internal clock is selected, the implied 
divisor is 16x, regardless of whatever divisor you may specify in the 
mode words.  AFAIK, when the internal clock is specified, pins 9 and 
25 turn into outputs.

I've used a 2661 with an external clock in async mode, and there the 
divisor (1x, 16x, 64x) matters.  But the 1x rate is a bastardized 
thing that doesn't really accommodate much speed variation between 
sender and receiver, unless the sender's also supplying the clock 
(similar to sync mode).  For general-purpose async use, it's best 
left out of the picture.

Cheers,
Chuck




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