Data Flow; Calculating Range - Mitsubishi Electric MELSEC iQ-RJ71EN71 User Manual

■Data flow

Data flow is used to specify the order of send data and receive data.
The data flow can be specified in forward direction (upper byte  lower byte), reverse direction (lower byte  upper byte),
and byte swap (by word).
• Forward direction, reverse direction: Available when the data length is 2 bytes or more.
• Byte swap: Available only when the data length is 4 bytes.

■Calculating range

Examples of specifying the length calculating range are shown below.
Packet
element 1
Packet format
Static data
Example 1
Example 2
Example 3
Example 1:Calculating range when start of range is set as 3 and end is set as 3
Example 2:Calculating range when start of range is set as 3 and end is set as 30
Example 3:Calculating range when start of range is set as 1 and end is set as 32
Non-conversion Variable
■Process procedure
The Ethernet-equipped module processes the non-conversion variable element with the following procedure.
When unit of stored data is "Lower Byte + Upper Byte"
• When the data length of a send packet is an odd number, the upper byte (lower byte when bytes are swapped) of the end
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.
Ex.
When sending data whose length is an odd number
(Word)
Data length storage area
Data storage area
APPX
402
Appendix 10 Operation Image and Data Structure of Predefined Protocol
Packet Packet
element 2 element 3
Non-conversion
Length
variable
Calculating
range for
the length
Calculating range for the length
Calculating range for the length
Specified device
+ 0 0005H
+ 1 0201H
+ 2 0403H
+ 3 0605H
Packet
element 30
Static data
Send data
No byte swap
06H 05H
↑
Data are not sent.
Sending
↓
05H 06H
Byte swap
Packet Packet
element 31 element 32
Static data Static data
04H 03H 02H 01H
03H 04H 01H 02H
External device