MOVITRAC
®
31.. PROFIBUS Fieldbus Interface
3 5
The PROFIBUS-DP
Interface
3
3 .7.3
Writing a Parameter via PROFIBUS-DP (Write)
When executing a WRITE service via the parameter channel, the handshake bit should not be tog-
gled until the entire parameter channel has been set up accordingly for the service in question, as
the parameter channel is transferred on a cyclic basis. Adhere to the following sequence of opera-
tions to write a parameter:
1.
Enter the index of the parameter to be written in byte 2 (Index High) and byte 3 (Index Low).
2.
Enter the data to be written in bytes 4...7.
3.
Enter the Service Identifier for the Write service in the management byte (byte 0).
4.
Transfer the Write service to the inverter by toggling the handshake bit.
The inverter now processes the Write service and returns the acknowledgement by toggling the
handshake bit.
01192AEN
Fig. 44: Coding of the WRITE service in the management byte
Fig. 44 shows how the WRITE service is coded in the management byte. The data length for all
SEW inverters is 4 bytes. Transfer of this service to the inverter is by toggling the handshake bit. A
WRITE service to SEW inverters therefore generally has the management byte code 32
hex
or 72
hex
.
3 .7.4
Sequence of Parameter Adjustment via PROFIBUS-DP
Using the WRITE service as an example, Fig. 45 shows the parameterizing sequence between
controller and inverter on PROFIBUS-DP. To simplify the sequence, only the management byte of
the parameter channel is shown in Fig. 45.
While the controller sets up the parameter channel for the Write service, the inverter simply receives
and returns the parameter channel. The service is first activated when the handshake bit has
changed, in this case from 0 to 1. The inverter then looks at the parameter channel and processes
the Write service, and responds to all messages, though with the handshake bit still = 0. Confirma-
tion that the service has been executed is indicated by the change of the handshake bit in the
response message from the inverter. The controller recognizes that the received handshake bit is
now the same as the one sent and can then prepare a new parameter adjustment.
0
0/1
1
1
0
0
1
0
Service identifier:
010 = Write
Reserved
Data length:
11 = 4 bytes
Handshake bit:
must be toggled for
each new service
Status bit:
0 = correct execution of service
1 = faulty execution of service
Byte 0: Management
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