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Setup Area Allocations Section 5-2
Clearing/Holding the
Contents of the
Reception Buffer in
Full-duplex Mode (Unit
Ver. 1.2 or Later Only)
Set to either clear (OFF) or hold (ON) the contents of the reception buffer
when the protocol macro starts.
OFF: Clear
When set to clear (OFF), the contents of the reception buffer will be cleared
when the protocol macro is executed.
ON: Hold
When set to hold (ON), the contents of the reception buffer will not be lost if
data acquisition fails after execution of the protocol macro.
This function prevents loss of data during full-duplex communications.
Data Conversion Timing
for Link Word
Specifications (Unit Ver.
1.2 or Later Only)
Set to perform I/O refresh upon request or continuously, as follows:
OFF: On-request I/O refresh (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.
ON: Continuous I/O refresh (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 Board/Unit is accessed during SEND/RECEIVE com-
mand execution. When the send command is executed with this method, the
actual message can be sent immediately.
Maximum Number of
Send/Receive Data Bytes
From 200 bytes up to a maximum of 1,000 bytes can be set in hexadecimal,
i.e., between 00C8 Hex and 03E8 Hex. Any setting below 00C8 Hex, will be
treated as 00C8 Hex; any setting above 03E8 Hex, will be treated as 03E8
Hex.
Note Flow Control and Maximum Number of Send/Receive Data Bytes
There is a 2.5-Kbyte reception buffer for each serial port in a Serial Communi-
cations Board or Unit. When using flow control, initiate flow control after
receiving about 2 Kbytes, and then release control after processing all but
0.5 Kbytes of receive data. Up to 1,000 bytes (500 words) of data can be
stored for each RECV command if 2 Kbytes of receive data is first stored in
the buffer and 1,000 bytes (03E8 Hex) is set as the maximum number of send/
receive data bytes.
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