Mitsubishi Electric MELSEC iQ-RJ71C24-R2 - Page 41

2 DATA COMMUNICATION USING PREDEFINED PROTOCOL
2.3 Packet
39
2
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.
■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.
*1 The unit of data length is byte.
+0
+n
Specified device
(Word)
Send packet: Users store the transmitted data
Data storage area
Receive packet: C24 stores the received data
+1
+n
+0
*1
Specified device
(Word)
Send packet: Users store the send data length (data length on the line)
Data length storage area
Receive packet: The C24 stores the receive data length (data length on the line)
Send packet: Users store the send data
Data storage area
Receive packet: The C24 stores the receive data