Publication 1734-UM009A-EN-P - June 2002
Configuring Your RS-232 ASCII Module 2-15
POINT I/O Parameters
Receiving Serial Data from the ASCII Device
The 1734-232ASC module receives a number of characters and
transmits these to the DeviceNet master via:
• I/O - poll, COS, or cyclic messages
• explicit message
The received character string is captured when:
• the specific number of bytes defined (Receive Character Buffer
Length) is received, or
• the defined End-of-String Terminator character is detected.
When either of these events occur, the 1734-232ASC module stores the
received message string into its internal buffer and will then transmit
(produce) it onto DeviceNet at the next appropriate opportunity.
Setting Up the Receive Character Buffer Length
The Receive Character Buffer Length is the number of characters that
the 1734-232ASC module can receive from your I/O device into its
buffer at one time. The length of the data string sent to the DeviceNet
master is less than or equal to this size, plus the 4-byte header.
If the 1734-232ASC module receives more characters than this number,
it will internally generate an overflow and force the data into the
1734-232ASC module DeviceNet transmit buffer to be sent to the
master. The subsequent received characters will then be received into
the buffer and handled at the start of the next incoming message
string. The overflow bit in the status byte will be set as well.
IMPORTANT
Incoming characters could be missed in the process
of handling a string longer than the
defined max
length.
This value can be set and retrieved by using the
standard set and get services on class 15 (F
hex),
instance 3, attribute 1.
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