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Operating Instructions – MOVITRAC® B
5
Communication and unit profile
Startup
Example: Writing a
parameter
(WRITE)
A parameter is written as it is read via the fieldbus interface (see figure below).
If the write service cannot be executed in the frequency inverter, for example because
incorrect parameter data were transmitted, the programmable controller will receive a
negative read response
. In this way, the programmable controller receives a negative
acknowledgement
(write error confirmation)
with exact identification of the error.
Writing a parame-
ter cyclically
For the cyclic transmission method, the handshake bit has to be changed to activate ser-
vice processing (execution of WRITE service). When using acyclic PDU types, every in-
verter processes every request telegram and in this way always executes the parameter
channel.
Parameters are set as follows:
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 and the data length for the write service in the manage-
ment byte (byte 0).
4. In cyclical PDU types, the WRITE service is not transferred to the inverter until the
handshake bit is changed. In acyclical PDU types, the parameter channel is always
evaluated.
The inverter now processes the write service and sends the service confirmation back
by changing the handshake bit.
5947132427
WRITE (8470: 2.5 s)
OK
Error + return code
CLIENT
SERVER
Write
request
Write
confirmation
Write error
confirmation
O R
negative
w rite response
Write response
Write indication
2b. Error occured!
No data written
2a. Parameter index
8470 is set to
2.5 s.
1. Write request (e.g. write the parameter value 2.5 s to index 8470 = rampe t11 to CW)
3a. Reply is sent o write service with the data (e.g. 0.5 s)
3b. Write service error, e.g. because the parameter value
is too high
00
I
Summary of Contents for Movitrac B
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