Connection to a fieldbus
6.4 Communication via RS485
Inverter with CU240B-2 and CU240E-2 Control Units
142
Operating Instructions, 07/2010, FW 4.3.2, A5E02299792B AA
The number of PZD words in a USS telegram is defined by parameter p2022. The first two
words are:
● Control 1 (STW1, r0054) and main setpoint (HSW)
● Status word 1 (ZSW1, r0052) and main actual value (HIW)
If P2022 is greater than or the same as 4, the additional control word (STW2, r0055) is
transferred as the fourth PZD word (default setting).
You define the sources of the PZD using parameter p2051.
For further information, please refer to the Parameter Manual.
6.4.2.8
Telegram monitoring
You require the telegram runtimes in order to set the telegram monitoring. The character
runtime is the basis of the telegram runtime:
Table 6- 26 Character runtime
Baud rate in bit/s
Transmission time per bit
Character run time (= 11 bits)
9600
104.170 µs
1.146 ms
19200
52.084 µs
0.573 ms
38400
26.042 µs
0.286 ms
115200
5.340 µs
0.059 ms
The telegram runtime is longer than just purely adding all of the character runtimes
(=residual runtime). The character delay time between the individual characters of the
telegram also has to be taken into account.
: : :
: : :
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Residual runtime
(compressed telegram)
50% of compressed
telegram residual runtime
Figure 6-17 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.