Mitsubishi Electric MELSEC iQ-R Series User Manual page 41

The following explains the configuration of the data storage area.
■When "Fixed Length/Variable Length" is "Fixed Length"
An area starting from the device number which is specified on the "Element Setting" screen is considered as the data storage
area.
The data storage area to be occupied varies depending on the setting of "Unit of Stored Data".
• When "Lower Byte + Upper Byte" is selected, the same size as the data length is occupied.
(However, when the data length of a send packet is an odd number, the upper byte (lower byte for "Byte Swap") of the last
device is not sent. When the data length of a receive packet is an odd number, the last data is stored with one byte of 00H
added.)
• When "Lower Bytes Only" is selected, twice the size of the data length is occupied.
Specified device
(Word)
+0
Data storage area
+n
■When "Fixed Length/Variable Length" is "Variable Length"
An area starting from the device number which is specified on the "Element Setting" screen +1 is considered as the data
storage area.
The data storage area to be occupied varies depending on the setting of "Unit of Stored Data".
• When "Lower Byte + Upper Byte" is selected, the same size as the data length + one word (length for the data length
storage area) are occupied.
(However, when the data length of a send packet is an odd number, the upper byte (lower byte for "Byte Swap") of the last
device is not transmitted. When the data length of a receive packet is an odd number, one byte of 00H is added to the last
data and stored.)
• When "Lower Bytes Only" is selected, twice size of the data length + one word (length for the data length storage area) are
occupied.
Specified device
(Word)
+0
Data length storage area
+1
Data storage area
+n
*1 The unit of data length is byte.
Send packet: Users store the transmitted data
Receive packet: C24 stores the received data
Send packet: Users store the send data length (data length on the line)
*1
Receive packet: The C24 stores the receive data length (data length on the line)
Send packet: Users store the send data
Receive packet: The C24 stores the receive data
2 DATA COMMUNICATION USING PREDEFINED PROTOCOL
2
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2.3 Packet