Siemens Sinamics G120P Operating Instructions Manual page 228

Operation
6.8 Communication via RS485
The telegram runtime is longer than just purely adding all of the character runtimes
(=residual runtime). You must also take into consideration the character delay time between
the individual characters of the telegram.
Figure 6-19
The total telegram runtime is always less than 150% of the pure residual runtime.
Before each request telegram, the master must maintain the start delay. The start delay
must be > 2 × character runtime.
The slave only responds after the response delay has expired.
Figure 6-20
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 6- 19
Baud rate in bit/s
9600
19200
38400
57600
115200
Note: The character delay time must be shorter than the start delay.
228
Telegram runtime as the sum of the residual runtime and character delay times
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
Min. start delay
> 2.291 ms
> 1.146 ms
> 0.573 ms
> 0.382 ms
> 0.117 ms
Inverter cabinet units
Operating Instructions, 12/2014, A5E32923362A