Hitachi SJ Series, User Manual

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14-1
Chapter 14 RS485 Communication
14
Chapter 14 RS485 Communication
Contents
14.1 What This Chapter Explains ..................... 14-1
14.2 Modbus-RTU ............................................ 14-2
14.2.1 Communication specification ................ 14-2
14.2.2 Wiring and Connection .......................... 14-2
14.2.3 Parameters ............................................ 14-5
14.2.4 Communication process ....................... 14-6
14.3 Message Structure ................................... 14-7
14.3.1 Queries and responses ......................... 14-7
14.3.2 Slave addresses (communication station
numbers) ............................................... 14-7
14.3.3 Function codes ...................................... 14-8
14.3.4 Data ....................................................... 14-8
14.3.5 Error check ............................................ 14-9
14.3.6 Time required for communication ........ 14-10
14.3.7 Responses in the normal condition ..... 14-10
14.3.8 Responses in the abnormal condition . 14-10
14.3.9 No response ........................................ 14-10
14.4 Description of Each Function code ........ 14-11
14.4.1 Reading out the state of coil [01h} ...... 14-11
14.4.2 Reading out the content of retention register
[03h] .................................................... 14-12
14.4.3 Writing to coil [05h] .............................. 14-13
14.4.4 Writing to retention register [06h] ........ 14-14
14.4.5 Loopback test [08h] ............................. 14-15
14.4.6 Writing to multiple coils [0Fh] .............. 14-16
14.4.7 Writing to multiple registers [10h] ........ 14-17
14.4.8 Writing and reading out to multiple registers
[17h] .................................................... 14-18
14.4.9 Exceptional Responses ...................... 14-19
14.4.10 Storing a change made to retention
register .............................................. 14-20
14.5 EzCOM Function .................................... 14-21
14.5.1 What is EzCOM? ................................. 14-21
14.5.2 EzCOM Settings .................................. 14-22
14.5.3 EzCOM Operation ............................... 14-23
14.5.4 Examples of EzCOM communication . 14-24
14.6 Lists of Coils and Communication Registers
........................................................................ 14-26
14.6.1 Preclusions at setting registers and coils
....................................................................... 14-26
14.6.2 List of coil numbers ............................. 14-27
14.6.3 List of retention register numbers ....... 14-28
14.1 What This Chapter Explains
This chapter describes the communication methods
operable using RS485 communication. PI main units
correspond to Modbus-RTU mode in which RS485 is
used as the physical layer.
Hitachi’s original EzCOM (communication between
inverters) function with Modbus protocol is also
available.
Select a communication function that you want to use
and configure it.
See “RS485 Communication Guide” for details of
functions such as message codes, function codes,
registers, and coils.
Make sure to carefully read “Chapter 1 Safety
Instructions/Risks” for safety work.
Symbol Meanings
General and troubleshooting
questions
Key points for a solution
Notes
Confirmation of procedures
Q
A
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