Precautions - Mitsubishi L02CPU User Manual

6.7

Precautions

(1) Send/receive packet
• When a message larger than 1460 bytes is sent from the external device using TCP, a packet may be
divided. As a result, data may not be received as one message with the predefined protocol function. Keep
the message less than 1460 bytes or use UDP.
• When data is received using TCP, separate data blocks that are sent successively may be combined at the
receiving side. Therefore, handshaking is required prior to communications.
(2) Predefined protocol setting
(a) To use two predefined protocol functions simultaneously (Ethernet or RS-
232/422/485)
Store the predefined protocol setting files in the same drive. If the setting files are stored separately in the SD
memory card and the standard ROM, the setting stored in the SD memory card is enabled while the setting
stored in the standard ROM is disabled.
To enable the predefined protocol setting stored in the standard ROM, format the SD memory card or delete
the predefined protocol setting stored in the SD memory card. Then, enable the setting.
The predefined protocol setting can be checked and deleted by operating the PLC user data.
[Online]
(b) After writing the predefined protocol setting
Power on or reset the CPU module, or turn on SM1355 (Predefined protocol setting check request) to enable
the written protocol setting data. If the written data are not enabled, the data may be changed unintentionally
when the CPU module is powered on or is reset.
(3) Device data
Data set by the predefined protocol function are communicated during the service processing. Therefore, if COM
instruction is executed while b15 of SD778 (Refresh processing selection when the COM/CCOM instruction is
executed) is on, data communications are also performed at the execution of the COM instruction.
(4) Connection with different open systems
Even the connection for which the open system is set to "Socket Communication" in parameter can be reopened
as the predefined protocol after the connection is closed. Similarly, the connection for which the open system is
set to "Predefined Protocol" in parameter can be reopened as the socket communication after the connection is
closed.
However, if the connection for which the open system is set to "Socket Communication" in parameter is reopened
as the predefined protocol after completion of closing, the status storage and protocol cancellation are not
possible since the start device to store the predefined protocol operation status cannot be specified.
CHAPTER 6 DATA COMMUNICATIONS USING THE PREDEFINED PROTOCOL
[PLC User Data] [Read] or [Delete]
6
63