Features; Serial Communications Units; Protocols - Omron CJ1W-SCU32 Operation Manual

1 Introduction
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Features

This section describes the features of the Serial Communications Unit and the protocols.
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Serial Communications Units

A total of up to 16 CPU Bus Units can be mounted on the CPU Rack or an Expansion Rack. The
total of 16 must include all Serial Communications Units and all other CPU Bus Units. The PLC can
thus be expanded to provide additional serial ports as required by the system.
There are two types of serial communications ports: RS-232C × 2 ports and RS-232C + RS-
422A/485 ports. If RS-422A/485 ports are used, general-purpose external devices are accessible
via 1:N connection (protocol macros) without using any Link Adapter.
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Protocols

Protocol Macros
The main features of the protocol macro functions are described below. For details, refer to the CX-Pro-
tocol Ver.1.9 Operation Manual (W344).
Wide Range of Communications Protocols
Communications are possible with virtually any general-purpose external device, provided it has an
RS-232C or RS-422A/485 port, supports half-duplex or full-duplex communications, and supports
start-stop synchronization.
Send Frames and Expected Receive Frames Matching Specifications
Send frames (command + data and other send frames) and expected receive frames (response and
other frames) can be created and registered according to the communications frame specifications
of the external device.
Communications-related Functions
Error check code calculations, frame length calculations during sending, and ASCII⇔Hexadecimal
conversion of numeric data are supported.
Send/Receive Monitoring
Receive wait monitoring, receive completion monitoring, and send completion monitoring are sup-
ported. If monitoring times are exceeded, send/receive can either be terminated, or retry processing
can be performed.
Retry Processing
Send/receive retry processing can be automatically executed when an error occurs, simply by set-
ting the number of retries.
PLC Read/Write Variables in Send Frames and Expected Receive Frames
You can include variables for reading PLC memory used for CJ-series Units in the actual send
frames. You can use these as destination addresses or data when you read PLC data during send-
ing. You can also include variables for writing to PLC memory used for CJ-series Units in the actual
receive frames. You can use these to write the contents of destination addresses or data to the PLC
during reception.
1-8 CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)