Siemens SIMATIC Distributed I/O System DP/ASi Link, Manual

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7-4
Distributed I/O System DP/ASi Link
EWA 4NEB 710 6055-02b
7.2 Normal Operation
In normal operation, the DP master exchanges data with the DP/ASi link in
exactly the same manner as with any other DP slave.
You do not have take any specific action.
In normal operation, there is a continuous exchange of data with the ASi and
the PROFIBUS-DP. The activities of the DP/ASi link can be divided into two
tasks:
1. Monitor the ASi
2. Monitor the PROFIBUS-DP
The task of the ASi monitor is to monitor and control communication within
the ASi. The input data from the ASi slaves are read and the output data are
written to the ASi slaves. The data are stored in the internal work memory.
The DP/ASi link simultaneously senses the actual configuration and
compares it with the setpoint configuration. If it is found to be different, a
diagnosis is prepared.
If the DP/ASi link is addressed by the DP master, the DP/ASi link transmits
the input data to the DP master and receives the output data for the ASi
slaves.
If an error is detected, the DP/ASi link generates a diagnosis, which is
fetched by the DP master (refer to Chapter 8).
If the ASi power supply fails during routine operation, the outputs of the ASi
slaves are reset. The input data are reset in the DP/ASi link and are not up-
dated until the power is restored.
Note
In the event of an ASi power failure, the data sent to the DP master by the
DP/ASi link are no longer valid.
Check, therefore, the data for validity by evaluating the slave diagnosis
(byte 12.4) and do not read them into your PLC until you have checked the
data.
Method of
operation
Tasks
Monitoring the ASi
Monitoring the
PROFIBUS-DP
Error detection
ASi power failure
Operating Modes