User Manual

Communication via RS485
5.3 Communication via USS
Fieldbuses
124 Function Manual, 04/2018, FW V4.7 SP10, A5E34229197B AE
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 5- 9 Duration of the start delay
Baud rate in bit/s
Transmission time per character (= 11 bits)
Min. start delay
9600
1.146 ms
> 2.291 ms
19200 0.573 ms > 1.146 ms
38400
0.286 ms
> 0.573 ms
57600
0.191 ms
> 0.382 ms
115200
0.095 ms
> 0.191 ms
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:
Response time of the slave to a request from the master
The response delay must be < 20 ms, but longer than the start
delay
•
Telegram runtime:
Transmission time of the response telegram sent from the slave
Telegram monitoring of the inverter
The inverter 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 inverter
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 inverter checks bit 10 of the received control word 1. If the
bit is not set when the motor is switched on ("Operation"), the inverter responds with fault
F07220.