ComAp InteliSys NTC Basebox Communications Manual page 136

Read Multiple Registers
Query
Byte
0 Controller address
1 3
Communication object number
upper byte (MSB)
2
lower byte (LSB)
3
Communication object length expressed by the number of
registers
4
upper byte (MSB)
5
lower byte (LSB)
Check field CRC
lower byte (LSB)
6
7 upper byte (MSB)
Standard response
Byte
0 Controller address
1 3
2 Length of read data in bytes (L)
Data of the 1st register
upper byte (MSB)
3
4 lower byte (LSB)
Data of the 2nd register
upper byte (MSB)
5
6 lower byte (LSB)
...
Data of the last register
upper byte (MSB)
L + 1
L + 2 lower byte (LSB)
Check field CRC
lower byte (LSB)
L + 3
upper byte (MSB)
L + 4
IGS-NT Communication Guide
Meaning
Meaning
1 to 32
Modbus function code
Greater than 0
see Check field calculation on
page 143
Same as in the query
Same as in the query
Number of registers *2
see Check field calculation on page 143
Note
Note
136