Hitachi WJ Series User Manual page 352

Chapter 11
11.2.11 Endian Selection of Holding Registers
 To change the endian (order of byte data) of Modbus communication data.
Q
 The communication endian is the byte data sequence of the communication 1-word data to be
A
transmitted and received. In WJ-C1, endian can be set for the data part of the transmit/receive
frame.
 Depending on the specifications of the external control equipment, it may be necessary to swap
the high byte and low byte of word data when reading/writing the holding register. You may not
need to process them by changing the endian selection. For details, refer to the instruction
manual of the external control equipment.
 Endian selection is valid only for read/write function codes (03h, 06h, 10h, 17h) of holding
!
registers and option commands (03h, 06h, 10h, 51h, 52h, 53h) in option communication. Also,
only the data part of the query/response is targeted.
 When using the inverter setting software ProDriveNext, set Endian selection to "Big Endian (00)"
(default). If it is set to other settings, it will not work properly.
 Endian selection does not function in the trip history monitor (register number 0012h to 004Eh)
and is read as big endian. When using the trip history monitor, set [P400] to "Big Endian". When
"Little endian" or "Special endian" is selected, perform data sorting appropriately when reading
data with an external control equipment, etc.
Code
[P400] Endian selection
Alignment of byte data for each endian setting
 Data order during Modbus communication for each setting is shown below, using one-word data
= 0102 h and two-word data = 01020304h as examples.
■ For 1 register length data
Send/receive byte order
1
2
■ For 2 register length parameter
Send/receive byte order
1
2
3
4
Item
The order of data section byte data is big endian.
The order of data section byte data is little endian.
The order of data section byte data is special endian.
Byte data array for Hitachi PLCs.
Big endian
01
02
Big endian
01
02
03
04
11-2-14
RS485 Communication
Description
Little endian Special endian
02
01
Little endian Special endian
04
03
02
01
Data
00
01
02
01
02
03
04
01
02