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OIT***-F113-B12-CB*
Communicating with the OIT system
7.1.1
For example: Successful read of a read-only tag
Below the communication between PLC and OIT system is more clearly illustrated
through a successful read cycle:
1. The PLC sends the command to the OIT system to read out the read-only
2. Depending on the settings, the OIT system either immediately captures an
3. At the end of the read operation, the PLC prompts resetting of the the OIT
This will end the complete read cycle.
7.1.2
Example: Read error in a read-only tag read
The communication for a read error between the PLC and the OIT system is
illustrated below:
1. The PLC sends the OIT system the command to read out a read-only tag
2. Depending on the settings, the OIT system either immediately captures an
3. Once the read operation has been repeated or the data has been manually
4. At the end of the read operation, the PLC prompts a reset of the the OIT sys-
30
tag ("Read to OIT" (SAH 1)).
image or the OIT system waits for a trigger signal and only then captures the
image.
After the successful image capture, the OIT system decodes the data stored
on the read-only tag and sends it to the PLC. At the same time, the OIT sys-
tem sends the message, "Wait for data" (STL 4) to the PLC.
system to the 'zero setting' with the command "Starting position to OIT"
(SAH 0)".
If a visualization of the process interface is to take place over OITControl,
then the following item may also be taken instead of item 3:
The PLC determines which data set matches the input data and sends it to
the OIT system together with the message "Current data to OIT" (SAH 2). If
the PLC does not find a matching data set for the data input from the OIT
system, the PLC will send the message "No data to OIT" to the OIT system
(SAH 3).
("Read to OIT" (SAH 1).
image or the OIT system waits for a trigger signal and only then captures the
image.
Once the image is captured, the OIT system determines a read error (the
LED Error lights up on the illumination unit of the device; i.e. the left display
area in OITControl in OIT LED status), and transfers the message "read er-
ror" (STL 2) to the PLC.
The read cycle is interrupted. Once the source of the error has been re-
moved, the read may be repeated. Otherwise, the data may be manually en-
tered.
entered, the OIT system will send the data to the PLC. At the same time, the
OIT system sends the message, "Wait for data" (STL 4), to the PLC.
tem to the 'zero setting' with the command "Starting position to OIT"
(SAH 0)".
If a visualization of the process interface is to take place through OITControl,
then the following may happen instead of item 3:
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