Configuring the fieldbus
7.6 Communication via RS485
Inverter with CU230P-2 Control Units
Operating Instructions, 11/2013, FW V4.6.6, A5E02430659B AG
159
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 7-15 Telegram runtime as the sum of the residual runtime and character delay times
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 7-16 Start delay and response delay
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 Duration of the start delay
Transmission time per character (= 11 bits)
Note: The character delay time must be shorter than the start delay.
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