3 4
MOVITRAC
®
31.. PROFIBUS Fieldbus Interface
3
The PROFIBUS-DP
Interface
Faulty Execution of Service
Faulty execution of service is signalled by setting the status bit in the management byte. If the
received handshake bit is identical to the transmitted handshake bit, the inverter has executed the
service. If the status bit indicates an error, the error code is entered in the data area of the parame-
ter message (Fig. 42). Bytes 4-7 provide the Return Code in a structured format (see the section
Return Codes).
01190AEN
Fig. 42: Structure of the parameter channel in the event of faulty execution of service
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
toggled 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
operations 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 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 manage-
ment 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.
01191AEN
Fig. 43: Coding of the READ service in the management byte
Fig. 43 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 inverter when the handshake bit is toggled. For example, the Read service could be activated
by entering the codes 01
hex
or 41
hex
in the management byte.
Byte 0
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
high
low
Status bit = 1: faulty execution of service
Management
Reserved
Index high
Index low
Error class
Error code
Add. code
Add. code
0
0/1
X
X
0
0
0
1
Service identifier:
001 = Read
Reserved
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
Byte 0: Management
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