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(2) Minimum delay time for PC link protocol transmission
For PC link protocol transmission instructions, the time from the point the instruction
is invoked to the point that instruction completes, that is the transmission delay time
from the point a transmission or reception request is initiated to the point the
response is received from the remote station will be as follows, assuming no
collisions occur on the network.
(Time from the point an instruction is invoked to the point that instruction completes
(in ms))
= (the S controller scan time (in ms)) + 25 ms + 0.035ms × (number of words
transmitted)
PC link protocol transmission differs from computer link protocol transmission in that
the PC link protocol processing/responding happens at the slave station at the point
the request occurs. Thus the PC link protocol transmission delay time does not
depend on the scan time at the slave station.
Usage Recommendations
• There are cases where the transmission delay time will be longer than the calculated value
due to details of the actual environment used. Factors that can cause the transmission delay
time to increase include network load, EN311 load (on both the local and remote stations),
and the S controller operating state.
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