Mitsubishi MELSEC LJ71C24, User Manual

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9 DATA COMMUNICATION USING THE PREDEFINED PROTOCOL
POINT
y When receiving variable length data whose length exceeds the "Maximum data
length", the C24 stores data as long as the maximum data length and omits the
rest. (A protocol completes successfully.)
y In receive packet data from other devices, the C24 needs to be able to
discriminate data corresponding to a Non-conversion variable from those of a
Terminator or a Static Data following a Non-conversion variable.
The receive process may not be performed normally if they cannot be classed.
(Example)
When value of a Terminator or value of a Static Data following a Non-conversion
variable is used in a Non-conversion variable, the C24 recognizes it as data of a
Terminator or a Static Data following a Non-conversion variable and performs the
verify/receive process.
y 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.
(a) Place any of the following data immediate after a Non-conversion variable
Static Data
Terminator
Check code + Static Data
Check code + Terminator
(b) Place a Length before a Non-conversion variable and include the Non-
conversion variable in the calculation range.
In addition, two or more of the following four elements cannot be placed in the
same packet.
Conversion variable (Variable number of data)
Conversion variable (Fixed number of data and Variable number of digits)
(Excluding a case where "Number of data" is '1' and "Delimiter" is not 'No
delimiter'.)
Non-conversion variable (Variable length)
Non-verified reception (Variable number of characters)