IFM Ecomat 300 AC1355, Supplementary Device Manual

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Acyclic services for Profibus DPV1
Description
10-1
10 Acyclic services for Profibus DPV1
10.1 Description
A main focus of the Profibus power stage DPV1 is the additionally available acyclic data transfer. Field
devices can be assigned parameters and calibrated during operation, and acknowledged alarm
messages are made possible. The transfer of the acyclic data is carried out in parallel to the cyclic
data transfer, but with a low priority.
There is read or write access via virtual slots and indexes. Via slots and indexes, access to data
blocks of up to 244 bytes is possible. With Siemens Step7, slot 0 is always assigned to the device
itself and can always be addressed.
• The controllere supports acyclic data transfer with DPM1 and DPM2 masters.
•
The access to parts of the data block in slot 0 is only possible by reducing the length. The offset of
the data is always 0 bytes for all data fields when access is made via slot 0 and index.
•
In case of a data length of 0, the entire length of the slot is returned. An error code is not returned
in case of length 0.
•
So, the M1 master flags can only be read in conjunction with the M1 digital inputs.
• In case of access via slot 0, index 10, the projected parameters (PP) can only be written in
conjunction with the projected configuration data (PCD).
•
Given that the Profibus FDT scheme (FDT =
F
ield
D
evice
T
ool) only allows access without length
indication, the controllere shortens the data blocks always to the maximum data length intended
for the slot/index. If the requested data length exceeds 160 bytes (= max. intended length in the
controllere), it is also reduced to the length of the requested data block.
WARNING
Danger due to outputs which are not switched off when the AS-i master or the AS-i connection fails!
For acyclic services, no cyclic repetition of the command is intended for system-related reasons.
There is no watchdog for acyclic services.
► Always start dangerous movements by means of
cyclic
services!