Vaisala HMP7 - Page 113

Writing pressure compensation value
Request Response
Bytes on the line
(hexadecimal)
Description Bytes on the line
(hexadecimal)
Description
(silence for 3.5 bytes) Start of Modbus RTU
frame
(silence for 3.5 bytes) Start of Modbus RTU
frame
F0
hex
Probe address F0
hex
Probe 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 54
hex
Modbus RTU
checksum
6E
hex
Value for first register
(least significant
word)
AD
hex
14
hex
44
hex
Value for second
register (least
significant word)
(silence for 3.5 bytes) End of Modbus RTU
frame
75
hex
4E
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
out-of-range values).
To verify that the value was
really accepted by the device,
read the register value after
writing.
AB
hex
(silence for 3.5 bytes) End of Modbus RTU
frame
Communication description
Register address 769 (1-based Modbus documentation format) =
0300
hex
(0-based format used in actual
communication).
Appendix A – Modbus reference
111