MOVIDRIVE
®
PROFIBUS DFP11A
29
The PROFIBUS-DP
Interface
3
3.7.2 Reading a Parameter via PROFIBUS-DP (Read)
When executing a READ 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 read a parameter:
1.
Enter the index of the parameter to be read in byte 2 (Index High) and byte 3 (Index Low).
2.
Enter the Service Identifier for the Read service in the management byte (byte 0).
3.
Transfer the Read service to the drive inverter by toggling the handshake bit.
As this is a Read service, the transferred data bytes (bytes 4 ...7) and the data length (in the man-
agement byte) are ignored and therefore do not need to be entered.
The inverter now processes the Read service and returns the acknowledgement by toggling the
handshake bit.
01230AEN
Fig. 28: Coding of the READ service in the management byte
Fig. 28 shows how the READ service is coded in the management byte. The data length is not rele-
vant so only the Service Identifier for the READ service has to be entered. The service is activated
in the drive inverter when the handshake bit is toggled. For example, the Read service could be
activated by entering the codes 01hex or 41hex in the management byte.
0
0/1
X
X
0
0
0
1
7
6
5
4
3
2
1
0
Byte 0: Management
Service identifier:
0001 = Read
Data length:
not relevant for Read service
Handshake bit
must be toggled for
each new service
Status bit
0 = correct execution of service
1 = faulty execution of service
X = not relevant
0/1 = bit value is toggled