Mitsubishi MELSEC LJ71C24, User Manual

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9 DATA COMMUNICATION USING THE PREDEFINED PROTOCOL
POINT
[For the fixed number of data]
y When "Number of Digits of Data" is "Variable Number of Digits", an invalid
number of digits error (7D19
H
) may occur if the number of digits of receive data is
0.
[For the variable number of data]
y A too few digits error (7D18
H
) may occur if data of which number of digits are
fewer than the digits specified in "Number of Digits of Data" are received.
(Example for the case that the setting of "Number of Digits of Data" is 4)
Receive Data
Conversion variable Terminator
"1" "2" "3" ETX
It is considered as an error that a
'Conversion variable' of the receive data
ends up with three digits while the setting of
"Number of Digits of Data" is four digits.
y When receiving data of which the number exceeds the "Maximum number of
data", the C24 stores data as many as the maximum number of data 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 Conversion variable from those of a
Terminator or a Static Data following a Conversion variable. The receive process
may not be performed normally if they cannot be classed.
(Example)
When a terminator or a fixed data value immediately after the Conversion
variable data is used as a Conversion variable, the C24 identifies it as the
terminator the fixed data value immediately after the Conversion variable data
and executes verification and reception.