Overview - Omron CQM1H-SCB41 Operation Manual

Overview

6-1

Overview

No-protocol
Specifications
100
Data can be sent or received without a protocol and without conversion by
connecting 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
attached to the data or the amount of data to be received can be specified.
The communications frame cannot be specified for no-protocol communica-
tions in the way it can be for protocol macros. Retry processing, data conver-
sion, and procedural branching according to received data are also not
possible. No-protocol 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
Messages (communications
frame)
Message transmissions
Message receptions
Maximum message length
Data conversion
Communications protocol
Transmission delay
Reception counter
Specification
One of the following.
Data only
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 1 to 256 bytes if transmis-
bytes sion ends in data (data only
or start code + data)
TXD( ) in ladder program
RXD( ) in ladder program
256 bytes including start code and end codes (253
bytes without start/end codes) for either sending or
receiving
None
None
0 to 99,990 ms (set in PC Setup in units of 10 ms)
The transmission delay is from the beginning of
TXD( ) execution until execution of the next TXD( )
can be started.
The number of bytes received at the port can be
counted from 0 to 256 bytes.
Section 6-1