Siemens Sinamics S110 Function Manual page 654

Communication
9.5 Communication using USS
Character delay time Off time between characters; must be less than 2x character runtime,
Start delay
Response delay
Residual runtime
"Slave transfer"/
"Master transfer"
The master must check the following times:
 "Response delay"
 "Residual runtime"
The slave must check the following times:
 "Start delay"
 "Residual runtime"
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Figure 9-55
The figure above shows the timeout ranges that have been verified on the USS slave. "crt"
means "Character run time". The maximum range is a factor of 1.5. "Start delay" and
minimum "Response delay" are values that are predefined in the software. The "Residual
runtimes" monitor values that can cause a timeout if they are exceeded on the receipt of
characters.
Process timeouts
Parameter p2040 determines the monitoring time for the received process data via the
fieldbus interface in ms. If no process data is received within this time, message F01910 is
output.
Monitoring is switched off if p2040 = 0.
652
but can also be zero
Off time between USS messages; must be > 2
Processing time of the slave; must be < 20 ms, but larger than the
start delay.
< 1.5 (n + 3)
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Sum of "Start delay", "Response delay" and "Residual runtime"
Response time of the slave to a USS request
Transmission time of the response telegram sent from the slave
Off time between USS messages
Transmission time for a request telegram coming from the master
Timeout checks on the USS slave
character runtime (whereby n = number of data bytes)
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Function Manual, 01/2011, 6SL3097-4AB10-0BP3
character runtime.
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Function Manual