Communications Overview - Omron K7DD User Manual

7-2

Communications Overview

Communications Method
This is a master/slave system in which multiple K7DDs (slaves) are connected to one host system
(master).
The K7DDs (slaves) connected to the same communications line are distinguished each other by a unit
number.
The commands sent by the master reach all the
slaves, but the unit number for respective slaves
is embedded in the command frame, which allows
the slaves to determine whether a command is
addressed to itself and to return a response only
to a command addressed to itself.
Refer to 3-7 Setting the Unit Number (P.3-16)
for information on how to set the unit number.
The host system (master) sends a command
frame, and the K7DD (slave) returns a response
frame corresponding to the command. One
command frame is paired with one response
frame.
The communications start with the master sending a command frame. Even if there is some change in
status that should be notified to the slave, it cannot be notified without an inquiry from the master.
Therefore, the master must poll at appropriate intervals to determine the slave status.
Power Line Data Generator User's Manual (N233)
7 Communications
No. 01 No.02
Response
from No. 02
No. 01 No.02
Host system Command frame
K7DD Response frame
Command to No. 2
Master
No.03
Master
No.03
Command frame
7 - 3
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