Specifications

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2.2.2 Fixed buffer communication
A PLC CPU can communicate with other PLC CPUs or a personal computer using the
fixed buffers in the buffer memory of the Ethernet module
A maximum of 1k words
of arbitrary data can be sent or received between PLCs or
between the PLC and the host system.
An Ethernet module has 16 fixed buffer data areas of 1k word storage space, and each
area is assigned as either a sending or receiving buffer for an arbitrary device.
While the communication using the MC protocol is passive, the communication using
the fixed buffers is the function for active communications.
Data can be sent from the PLC CPU side to the host system when a mechanical error
occurs or when some conditions are satisfied.
Furthermore, by using interrupt programs in data reception, retrieval of receive data to
the PLC CPU may be expedited.
Error occurred!
PLC CPU (Local station)
Error confirmed!
Error confirmed!
PLC CPU
Personal computer
(1) Control method
The fixed buffer areas in the Ethernet module are used to communicate with an
external device.
PLC CPU
No.1
No.2
No.3
No.4
No.16
Send
External device
Receive
Buffer memory
Fixed buffer
BUFRCV
instruction
BUFSND
instruction
to