5.1.2
Data Length/Coding
The parameter data length for MOVITRAC
®
31.. frequency inverters amounts to a constant 4 bytes
for all parameters. You can find detailed information about data length and coding as well as
information on minimums and maximums in the
MOVITRAC
®
31.. Parameter List.
5.2
Reading a Parameter (READ)
Reading a parameter via the fieldbus interface is carried out using a
Read Request from the
automation equipment to the MOVITRAC
®
31.. frequency inverter. When it receives this read request,
the inverter is instructed to read the drive parameter of the index transferred (
Read Indication). The
service is then carried out in the inverter, and if the run is fault-free, the data are returned to the
higher-level automation equipment in response (
Read Response). The Read service is ended on
receipt of confirmation of the service (
Read Confirmation) by the automation equipment.
If it is impossible to carry out the Read service in the inverter, this is reported back to the automation
equipment by a negative answer
(Negative Read Response). The automation equipment thus receives
a negative confirmation
(Read Error Confirmation) with a detailed breakdown of the error.
MO
VI
TR
AC
®
841
E
Q
RUN
BUS
FAULT
Master
Slave
Read (1025)
FIELDBUS
CONTROL MODE
Read error
confirmation
Error + return code
Negative
read response
2b. An error has occurred!
No data available
OR
O.K. + data of index 1025
3b. Read service faulty, for further information see return code
Read
confirmation
Read response
Read indication
Read
request
3a. Inverter responds to read request sending requested data (e.g. 0.5 s)
1. Read request (e.g. Read T11 ramp up = index 1025)
2a. Parameter index 25
(1025-1000) is read
by inverter.
00334AEN
Fig. 27: Reading a parameter
5
Setting Inverter Parameters
MOVITRAC
®
31.. Fieldbus Unit Profile
47
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