How long does it take for a PCD7.L1xx or a PCD7.L3xx module to respond to an S-Bus telegram?

FAQ #100869

When values are read from a PCD7.L1xx or a PCD7.L3xx module, the preparation of the S-Bus response telegram needs about 10 ms. This time is longer than the same task does take on a PCDx.Mxxx CPU. The time used for writing a value to a PCD7.Lxxx module is about equal to the time that is used by a PCDx.Mxxx CPU (because only an acknowledgement needs to be replied).

 

Symptom
The communication cycle time for reading e.g. 4 bits from some PCD7.Lxxx modules is higher than the communication cycle time for reading the same amount of data (with the same number of telegrams) from PCDx.Mxxx CPUs.

Reason
This phenomenon is caused by the fact that a PCD7.Lxxx (e.g. a PCD7.L100) has a slower processor than a PCDx.Mxxx CPU. The preparation of an S-Bus telegram does therefore take longer (about 10 ms per response).

Remark
This rule does only apply when reading from a PCD7.L1xx or a PCD7.L3xx module. The treatment of requests for writing values (outputs) to the module is much faster (because only a "simple" acknowledgement needs to be responded). 

 

Categories

PCD7 / Lxxx

Last update: 27.05.2015 21:01

First release: 24.01.2008 16:19

Views: 2415

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