Precautions - Mitsubishi Electric MELSEC-L SERIES Basic User Manual

12.8.3

Precautions

This section describes the precautions for broadcast communications.
(1) Port number
To perform broadcast communications, the user needs to determine the port numbers dedicated for data
sending/receiving for broadcast communications and specify these port numbers.
(2) Size of send/receive data per sending/receiving
A maximum of 2046 bytes of data in the application data can be processed per sending/receiving. To send data
with a size exceeding 2047 bytes, divide the data into smaller chunks at the send source.
Remark
An E71 temporarily stores a subsequent receive data in its internal buffer for the operating system until the current receive
process is completed. If data with a size exceeding the capacity of the internal buffer (approximately 40KB) is received by
broadcast communications, the data is discarded. In communications using a fixed buffer in the "Procedure Exist" control
method, the E71 sends a command message to the connected device, waits for a response message, then sends the next
command message. Therefore, the user need not take account of the above-mentioned internal buffer for the operating
system.
CHAPTER 12 COMMUNICATIONS USING A FIXED BUFFER
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