Siemens SINAMICS G120 Operating Instructions Manual page 168

Configuring the fieldbus
7.7 Communication via RS485
The slave only responds after the response delay has expired.
Figure 7-17
The duration of the start delay must at least be as long as the time for two characters and
depends on the baud rate.
Table 7- 16
Baud rate in bit/s
9600
19200
38400
57600
115200
Note: The character delay time must be shorter than the start delay.
Telegram monitoring of the master
With your USS master, we recommend that the following times are monitored:
• Response delay:
• Telegram runtime:
Telegram monitoring of the converter
The converter monitors the time between two requests of the master. Parameter p2040
defines the permissible time in ms. If a time p2040 ≠ 0 is exceeded, then the converter
interprets this as telegram failure and responds with fault F01910.
150% of the residual runtime is the guide value for the setting of p2040, i.e. the telegram
runtime without taking into account the character delay times.
For communication via USS, the converter checks bit 10 of the received control word 1. If the
bit is not set when the motor is switched on ("Operation"), the converter responds with fault
F07220.
168
Start delay and response delay
Duration of the start delay
Transmission time per character (= 11 bits)
1.146 ms
0.573 ms
0.286 ms
0.191 ms
0.059 ms
Response time of the slave to a request from the master
The response delay must be < 20 ms, but longer than the start delay
Transmission time of the response telegram sent from the slave
Min. start delay
> 2.291 ms
> 1.146 ms
> 0.573 ms
> 0.382 ms
> 0.117 ms
Converter with the CU250S-2 Control Unit (vector)
Operating Instructions, 06/2013, FW V4.6, A5E31759476B AB