Read Holding Registers (Query Using Fc = 03H) - IAI RoboNet Operation Manual

3.9.3.3

Read Holding Registers (Query using FC = 03H)

This query reads the contents of holding registers in the slave. Broadcast is not supported.
The basic query/response structures and examples of queries are shown below.
(1) Basic Query/Response Structures
[1] Query format
The query message specifies the address of the holding register (gateway register) from which to start reading data,
and the number of registers.
Data length of 1 holding register = 1 word = 2 bytes = 16 bits
Field name
Header
Slave address
Function code
Starting address
Starting address
Number of registers
Number of registers
Error check
Trailer
Total bytes
[2] Response format
Field name
Header
Slave address
Function code
Data bytes
Data 1
Data 1
Data 2
Data 2
Error check
Trailer
Total bytes
RTU mode data
(8 bits)
None
3F H
03 H
(upper) Arbitrary
(lower) Arbitrary
(upper) Arbitrary
(lower) Arbitrary
CRC (16 bits)
None
RTU mode data
(8 bits)
None
3F H
03 H
Arbitrary
(upper) Arbitrary
(lower) Arbitrary
(upper) Arbitrary
(lower) Arbitrary
CRC (16 bits)
None
Data length
(bytes)
-
1 Fixed.
1
The address varies depending on the axis
2
arrangement.
2 Refer to the query list.
2
-
8
Data length
(bytes)
-
1 Fixed.
1
Number of registers specified in the query
1
format x 2
1 each for upper
and lower words
2 Data corresponding to the data bytes (number
of specified registers x 2)
Same as above
2
-
Part 1 Specification
Remarks
Remarks
119