>-----Original Message-----
>From: piclist-bounces@mit.edu [mailto:piclist-bounces@mit.edu] 
>On Behalf Of Gerhard Fiedler
>Sent: 26 February 2007 14:06
>To: piclist@mit.edu
>Subject: Re: [PIC] Timeless communication protocols
>
>
>Michael Rigby-Jones wrote:
>
>> From Forrest W Christian
>>> 
>>> I'm 99.9% sure I can do bidirectional, half-duplex 
>no-timing-needed, 
>>> digital-realm communications with 2 open-collector outputs 
>capable of 
>>> self-read.
>> 
>> A slightly adpated I2C multi-master system would acheive 
>this I think, 
>> i.e Master becomes a slave after finishing it's transmission.
>
>Wouldn't this require that the current slave (receiver) can 
>follow the current master's (sender's) clock speed? There's 
>the clock extension thing, but this works only in one clock 
>direction, and need to come before it's too late.

Clock stretching works in the direction that's important, i.e. the slave can bring the speed of the master down to wherever it feels comfortable.  However the fact that only whole bytes are acknowledged rather than individual bits means that it's probably less suitable as a polled software only protocol between devices with widely differing speeds.  Using an external interrupt for the incomming clock would fix this.

Regards

Mike

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