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Old March 29th, 2007   #2
Task Group Member
Join Date: Jun 2006
Posts: 181


This is a maximum allowed time for the MAB. If you are greater than this, you are not compliant. The restrictions on times were designed to keep RDM traffic "tight" and reduce the impact on the throughput of null start code packets. If, as you suggest, your system cannot meet this time you cannot claim compliance, as the spec currently stands.

What your are suggesting is that your system can have (presumably intermittently) up to 88us of intercharcter delay ... which seems unusually high. A necessary approach may be to mask interrupts accordingly to keep the MAB short, or rejig priority levels. Once you have sent the start code (and thus completed the MAB), there is more slack on interbyte time.

Please dont forget RDM also places a restriction on the total packet time.

Can you elaborate on your particular hardware/system that exhibits this problem ?

Exceeding the spec for the extra 40us you propose WOULD be a potential tragedy, as someone else might legimately reject your packet based on receipt of what is (to them as per the spec) an illegally timed packet. Unlikely perhaps, but possible and legitimate.

This was not (to my knowledge) ever flagged as an issue during public review.

Peter Willis
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