Appendix A. Modbus Registers
The Modbus registers available for HMD65 include measurement output registers in metric and
non-metric units, pressure compensation setpoint configuration, status registers, and
communication test registers.
The Modbus communication settings are configured using the DIP switches on HMD65
component board: see Modbus and BACnet Overview (page 26).
Registers are numbered in decimal, starting from one. Register
addresses in actual Modbus messages (Modbus Protocol Data Unit (PDU)) start
from zero.
Please check the reference documentation of your Modbus host (PLC) for the
notation of Modbus register addresses.
CAUTION!
16-bit integers have a maximum value of +32767. Certain measurement
parameters can exceed this value when x100 scaling is used (see measurement
registers 0100
hex
… 0107
hex
and 0180
hex
… 0187
hex
). Whenever possible, it is
recommended to use 32-bit float values.
A.1 Measurement Data Registers
Table 12 Modbus Measurement Data Registers (Read-Only)
Register
Number
(Decimal)
Address
(Hexadecimal)
Register Description Data Format Unit
Floating Point Values (Metric)
1 0000
hex
Relative humidity 32-bit float %RH
0001
hex
3 0002
hex
Temperature 32-bit float °C
0003
hex
5 0004
hex
Dew point temperature 32-bit float °C
0005
hex
7 0006
hex
Dew/frost point
temperature
32-bit float °C
0007
hex
HMD65 User Guide M212243EN-A
48
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