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From: rando@skipper.dfrf.nasa.gov (Randy Brumbaugh)
Newsgroups: comp.sys.transputer
Subject: Link Sync Kink = Jynx??
Keywords: link
Message-ID: <856@skipper.dfrf.nasa.gov>
Date: 4 Apr 91 23:45:39 GMT
Organization: NASA Ames-Dryden FRF, Edwards, CA
Lines: 29

My question is concerning hardware link communication.  I would 
appreciate any help or experiences.

The story:
There are 2 t800s, "A" and "B".  They are connected by a link.
A uses robust (time-out guarded) link i/o.  B does not.

A sends a 1-byte command to B.  B is not ready, so A times out
and gives up and retries, repeatedly.  Eventually B gets ready and tries
to read a byte from the link.

My question(s):

Is there a time period when B can read the command and try to
respond, even after A has timed out and given up?

Should A reset the link after each time-out?

When B gets ready, should it do a channel reset to be
sure the link is "clear" before trying to to read?

This is based on a true story.  In the application, 
B takes about 4 seconds before it is ready to accept a
command byte from A.  If A tries before the 4 seconds,
it never works.  When we put a 5 second delay in the A
process, so it waits until B is ready before trying to
communicate, it seems fine.  Not sure why this is.

Randy Brumbaugh  rando@skipper.dfrf.nasa.gov