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Introduction
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M2M Gateway PLC Communication Settings
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6.
PLC Communication Outline
This section describes the general outline on PLC communication before configuring the
CONPROSYS M2M Gateway settings.
PLC Communication : Command Response Method
Each PLC has its own protocol of the maker for external communication. Generally, a master (a remote
device such as M2M Gateway) makes a request and receives a response from a slave (PLC).
When collecting information, the master makes a request to the slave by specifying the device
address type and the range, then obtains device values from the PLC.
When specifying data (writing), the master transmits the device address information and values, then
receives a completion response from the PLC.
- An example of data request
- Communication Command
Some PLCs have a function to access areas with gaps at one time using the random access function.
However, the M2M Gateway has no such a function, therefore, an alternative measure is used to
access continuous areas, instead.
In order to access the area with gaps, it is necessary to perform communication several times.
For information collection performances, consider placing the collected data side by side or arranging
the access settings, for instance.
- There are gaps in the access area - Collecting data by performing communication several times.
- Arrange data order
D memory : request 0-99
Response of memory info
PLC
M2M Gateway
*Communication permission or parameter change might be
required depending on PLCs or communication styles.
PLC Memory
・・・
PLC Memory
Copy data into empty addresses that are alligned sequentially
* Communication performance can be improved and access with
the same scan can be realized.
Obtain data at one time communication
Group 1
Group 2
Group 3
Group 4