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CHAPTER 11 DATA COMMUNICATIONS USING THE PREDEFINED PROTOCOL
11
11.3 Packet Elements
*1 Do not set local devices.
*2 Set within the device range specified in the "Device" window of PLC Parameter.
The following describes the configuration of the data storage area.
(a) When "Fixed Length/Variable Length" is "Fixed Length"
An area starting from the device number which is specified in the "Element Setting" window 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 00
H
.)
• When "Lower Bytes Only" is selected, twice the size of the data length is occupied.
Data Storage Area
Specification
Specify a start device to store variable value.
Available devices are as follows:
• Internal user
*1*2
Input relay (X)
Output relay (Y)
Internal relay (M)
Latch relay (L)
Link relay (B)
Data register (D)
Link register (W)
• File register
*2
File register (R, ZR)
• Buffer memory
G device (G) (Send/receive area for predefined protocol support function (address: 4800
H
to 4FFF
H
))
Item Description
Data storage area
Specified device
+ 0
+ n
(Word)
Send packet: The user stores the send data.
Receive packet: The E71 stores the receive data.
Send
packet
Data storage area
Receive
packet
Data storage area
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