Omron CQM1H-SCB41 operation manual No-protocol Specifications

Using No-protocol Communications Section 6-1

6-1 Overview

No-protocol Specifications

Data can be sent or received without a protocol and without conversion by con- necting an external device to the RS-232C port and executing the TXD(––) or RXD(––) instruction from the ladder program. Start and end codes can be at- tached to the data or the amount of data to be received can be specified.

The communications frame cannot be specified for no-protocol communications in the way it can be for protocol macros. Retry processing, data conversion, and procedural branching according to received data are also not possible. No-pro- tocol communications are thus good for communicating with bar code readers and other external devices with RS-232C ports that do not required command- response procedures. Data is sent in one direction only, using TXD(––) to send data from the port or RXD(––) to read data received on the port.

Note When TXD(––) is executed in No-protocol Mode, data from I/O memory is sent from the port without conversion. When TXD(––) is executed in Host Link mode (for slave-initiated communications), the contents of the specified words in I/O memory is converted to ASCII before being sent.

The specifications of no-protocol communications are given in the following table.

Item	Specification
Messages	One of the following.
(communications	Data only
frame)
	Start code + data
	Data + end code
	Start code + data + end code
	Data + CR + LF
	Start code + data + CR + LF
	Settings are made in the PC Setup: Start code enable, end
	code enable, start code, end code, number of receive bytes
	(when end code is disabled)
	Start code	Disabled or 00 to FF Hex
	End code	Disabled, 00 to FF Hex, or
		CR+LF
	Number of receive bytes	1 to 256 bytes if transmission
		ends in data (data only or start
		code + data)
Message	TXD(––) in ladder program
transmissions
Message	RXD(––) in ladder program
receptions
Maximum	256 bytes including start code and end codes (253 bytes
message length	without start/end codes) for either sending or receiving
Data conversion	None
Communications	None
protocol
Transmission	0 to 99,990 ms (set in PC Setup in units of 10 ms)
delay	The transmission delay is from the beginning of TXD(––)
	execution until execution of the next TXD(––) can be started.
Reception counter	The number of bytes received at the port can be counted from
	0 to 256 bytes.

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