Mitsubishi Electric MELSEC iQ-R Series User Manual page 42

Precautions
● When receiving variable length data whose length exceeds the "Maximum data length", C24 stores data as long as the
maximum data length and omits the rest. (A protocol completes successfully.)
● Out of packet data received from target devices, the data corresponding to variable needs to be discriminated from a
terminator or a static data immediately after non-conversion variable. The reception processing may not be performed
normally if they cannot discriminated.
Ex.
When value of a terminator or value of a static data following a non-conversion variable is used in a non-conversion variable,
C24 recognizes it as data of a terminator or a static data following a non-conversion variable and performs the verification/
reception processing.
● Multiple Non-conversion variable (Fixed length) elements can be placed in a packet, and multiple Non-conversion variable
(Variable length) elements can also be placed in a send packet. However, only one Non-conversion variable (Variable length)
can be placed in a receive packet, and any of the following requirements need to be met.
• Place any of the following items immediate after the non-conversion variable.
Static Data
Terminator
Check code + Static Data
Check code + Terminator
• Place a Length before a Non-conversion variable and include the Non-conversion variable in the calculating range.
In addition, two or more of the following four elements cannot be placed in the same packet.
• Variable number of data [Conversion variable]
• Fixed number of data and variable number of digits [Conversion variable] (Excluding a case where "Number of Send Data"
is '1' and "Delimiter" is not 'No delimiter'.)
• Variable length [Non-conversion variable]
• Variable number of characters [Non-verified reception]
2 DATA COMMUNICATION USING PREDEFINED PROTOCOL
40
2.3 Packet