ComAp InteliSys NTC BaseBox

IGS-NT Communication Guide
133
Read Multiple Registers
Query
Byte Meaning Note
0-1 Transaction Identifier
Value will be copied into
response.
2-3 Protocol Identifier 0 = MODBUS protocol
4-5 Number of following bytes
4 + 2 * Number of
registers.
6 Controller address 1 to 32
7 3 Modbus function code
8
9
Controller address
upper byte (MSB)
lower byte (LSB)
10
11
Communication object length expressed by the number of registers
upper byte (MSB)
lower byte (LSB)
Greater than 0
Standard response
Byte Meaning Note
0-1 Transaction Identifier Value from query
2-3 Protocol Identifier 0 = MODBUS protocol
4-5 Number of following bytes
3 + 2 * Number of
registers.
0 Controller address Same as in the query
1 3 Same as in the query
2 Length of read data in bytes (L) Number of registers *2
3
4
Data of the 1st register
upper byte (MSB)
lower byte (LSB)
5
6
Data of the 2nd register
upper byte (MSB)
lower byte (LSB)
...
L + 1
L + 2
Data of the last register
upper byte (MSB)
lower byte (LSB)