Omron CQM1H-CLK21 - Manual (Page 29)

6
Overview Section 1-1
Data Links
Data links allow the constant sharing of data in predetermined data areas
between nodes, between PLCs, or between a PLC and an IBM PC/AT or com-
patible computer on the network. Data links do not require the use of commu-
nications programs on the PLC (CPU Unit) or IBM PC/AT or compatible
computer. Data written in the send area of the local node will be automatically
sent to the receive area of other nodes.
The I/O area (CIO area), link area (LR area), DM Area area (DM area), and
extended DM Area area (EM area) can be freely set in the send or receive
area. (The area used for sending or receiving data using the data link function
is called “data link area.”)
The data link area can be set automatically or manually.
Automatic Setting Used for simple data link processing. Data link can be performed by simply
setting parameters in the DM area of the PLC.
Send data size per node is the same for all nodes. All nodes participating in
the data link share the same data.
Manual Setting Used for flexible data link processing depending on each system.
Using the Controller Link Support Software, individual data link tables can be
set for each node and the data link area can be freely allocated for each node.
Send data size per node can be freely set. It is also possible to set nodes for
only send or receive data. With the Controller Link Unit, the data link can be
set to receive only a part of the data link area of other nodes.
Message Service
This function controls data transmission with particular nodes, reading or writ-
ing of status data, changing of operation modes, etc., by executing communi-
cations instructions on a program. The communications instructions include
SEND/RECV instructions for data transmission and CMND instructions for
issuing various commands.
Controller Link Unit
Constant data exchange (sharing)
PLC PLC PLC
Data transmission (under certain conditions)
as required
User program
Communications instruction
Controller Link Unit
PLC PLC PLC