Vaisala HUMICAP HMM170 - Appendix B. FCC Part 15 Compliance Statement; FCC Part 15 Compliance Statement

Writing pressure compensation value
Request Response
Bytes on the line Description Bytes on the line Description
(silence for 3.5 bytes) Start of Modbus RTU
frame
(silence for 3.5 bytes) Start of Modbus RTU
frame
F0
hex
Device address F0
hex
Device address
10
hex
Function (Write
Multiple Registers)
10
hex
Function (Write
Multiple Registers)
03
hex
Register address 03
hex
Register address
00
hex
00
hex
00
hex
Number of registers to
write (2)
00
hex
Number of 16-bit
registers written (2)
02
hex
02
hex
04
hex
Number of data bytes AD
hex
Modbus RTU
checksum
6E
hex
Value for first register
(least significant
word)
54
hex
14
hex
44
hex
Value for second
register (most
significant word)
(silence for 3.5 bytes) End of Modbus RTU
frame
75
hex
AB
hex
Modbus RTU
checksum
The response to a write
function informs that the
function was correctly received
by the device. It does not
guarantee that the written
value was accepted by the
device (for example, in case of
out-of-range values).
To verify that the value was
really accepted by the device,
read the register value after
writing.
4E
hex
(silence for 3.5 bytes) End of Modbus RTU
frame
Communication description
Register number 769 (1-based Modbus register number) = address 0300
hex
(0-based address
used in actual communication).
Data format Two 16-bit Modbus registers interpreted as IEEE 754 binary32 floating point
value, least significant word first.
Appendix A – Modbus reference
45