Siemens SINAMICS G120 Operating Instructions Manual page 231

Character delay time timeout between characters and must be smaller than 2 time the
Start delay
Response delay
Residual run time
"Slave
Transmitting"/
"Master
Transmitting"
The master must check the following times:
• "Response delay"
• "Residual run time"
The slave must check the following times:
• "Start delay"
• "Residual run time"
: : :
Figure 8-25
The timeout margins that are verified on the USS slave are shown in the figure above. "crt"
stands for "character run time". The factor "1.5" is the maximum margin. The "start delay"
and the minimum "response delay" are fixed minimum values in software. The "residual run
times" are monitoring values that cause a timeout if they are exceeded by the character
reception.
Control Units CU240S
Operating Instructions, 11/2006, A5E00766042B AA
character run time but can be zero
timeout 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)
*
is the sum of "Start delay", "Response delay" and "Residual run
time"
= reaction time of slave to USS request
= transmission time of response telegram sent by slave
= timeout between USS messages
= transmission time of request telegram coming from master
Timeout Checks on USS Slave
character run time (where n = number of data bytes)
*
: : :
Functions
8.7 Communication via USS
character run time
*
: : :
8-35