Omron CJ1W-SCU32 Operation Manual page 154

4 Using Protocol Macros
Clearing/Holding the Contents of the Reception Buffer in Full-duplex Mode
Set to either clear or hold the contents of the reception buffer when the protocol macro starts.
FALSE: Clear
When set to clear, the contents of the reception buffer will be cleared when the protocol macro is
executed.
TRUE: Hold
When set to hold, the contents of the reception buffer will not be lost if data acquisition fails after
execution of the protocol macro.
This enables you to hold the data in the reception buffer received in the previous communications
sequence after you switch the communications sequence during full-duplex communications.
This function prevents loss of data during full-duplex communications.
Data Exchange Method for Link Words
Set to perform I/O refresh upon request or continuously, as follows:
FALSE: On-request I/O refreshing (Immediate refresh mode)
Data exchange is performed during I/O refresh when a refresh request is sent to the CPU Unit for
each Send/Receive command that is executed. A time delay will occur after the Send command is
executed until the actual message is sent when this method is used.
TRUE: Continuous I/O refreshing (Cyclic refresh mode)
During protocol macro execution, I/O refreshing is continuously performed with the CPU Unit, the
data in the link word area is refreshed from the CPU Unit, and the data in the Unit is accessed dur-
ing Send/Receive command execution. When the Send command is executed with this method, you
can send the actual message immediately.
Maximum Number of Bytes in Protocol Macro Send/Receive Data
You can set bytes from 200 bytes to a maximum of 1,000 bytes.
Any setting below 200 bytes will be treated as 200 bytes; any setting above 1,000 bytes will be
treated as 1,000 bytes.
Set this value to the maximum 1,000 bytes when you use the standard system protocol.
Additional Information
Flow Control and Maximum Number of Send/Receive Data Words
There is a 2.5 KB reception buffer for each serial port in the Serial Communications Unit.
When flow control is used, initiate flow control after receiving about 2 KB, and then release con-
trol after processing all but 0.5 KB of receive data.
The Unit can store up to 1,000 bytes (500 words) of data for each Recv command if 2 KB of
receive data is first stored in the buffer and 1,000 bytes is set as the maximum number of
send/receive data bytes.
4-18 CJ-series Serial Communications Units Operation Manual for NJ-series CPU Unit(W494)