Hitachi SJ7002 Series Instruction Manual page 306

B–22
ModBus Mode Communications
Message Config-
uration: Query
Each frame is formatted as follows:
Frame Format
Header (silent interval)
Slave address
Function code
Data
Error check code
Trailer (silent interval)
Slave address:
• This is a numer from 1 to 32 assigned to each inverter (slave). (Only the inverter having the
address given as a slave address in the query can receive the query.)
• When slave address "0" is specified, the query can be addressed to all inverter simultane-
ously (broadcasting).
• In broadcasting, the host (master) cannot read inverter data nor perform a loopback test.
Data:
• The data contains a function command.
• The data format used in the SJ700
Name of Data
Coil Binary data that can be referenced and changed (1 bit long)
Holding Register 16-bit data that can be referenced and changed
Function Code:
Specify a function you want to make the inverter execute. Function codes available to the
SJ700 are listed below.
2
Function
Function
Code
01h Read Coil Status
03h Read Holding Register
05h Write in Coil
06h Write in Holding Register
08h Loopback Test
0Fh Write in Coils
10h Write in Registers
Error check:
Modbus-RTU uses CRC (Cyclic Redundancy Check) for error checking.
• The CRC code is 16-bit data that is generated for 8-bit blocks of arbitrary length.
• The CRC code is generated by a generator polynomial CRC-16 (X
corresponds to the ModBus data format below.
2
Description
Maximum data size
(bytes available per
message)
4
8
2
2
—
4
4
Maximum number of
data elements per
message
32 coils (in bits)
4 registers (in bytes)
1 coil (in bits)
1 register (in bytes)
—
32 coils (in bits)
4 registers (in bytes)
16 15 2
+ X + X + 1).