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Appendices
Appendix B - MD-BMS and MD-BMED Power Meters Modbus Absolute/Net Value Measurement Registers and
Protocol Commands
86
Building Technologies
125-202
06/06/2017
Modbus
Offset
Register
Description
47061
7060
Volts L3 to Neutral
“
47062
7061
Time Since Reset LSW (Seconds) Seconds since kWh, kVAh, kVARh and
associated Demand registers were reset. LSW
(resettable).
47063
7062
Time Since Reset MSW (Seconds) Seconds since CAM. MSW
47080
7079
Negative kW System Average
Equals Negative KWH_SYSTEM_L&M ÷
(TimeSinceReset_L&M seconds /3600
seconds/Hr) (resettable).
46081
7080
Negative kW Demand System
Minimum
Minimum Average power window (kW)
47082
7081
kVA Demand System Maximum
Maximum Instantaneous kVA Demand (kW,
resettable).
47083
7082
kVA Demand System Now
System Average kVA Demand for the most
recent (current) Demand Window (resettable).
47084
7083
kVAR Demand System Max
System Maximum kVAR Demand (kVAR,
resettable). It displays the default value after a
CAM until one demand window elapses. After a
power cycle or CPU reset, the value is not reset
and does not update again until one demand
window elapses.
Protocol Commands
The Modbus messaging protocol used for communication follows the Modbus RTU
protocol described in this section. Each register read from or written to the power
meters is a 16-bit, unsigned, positive integer value. The MD-BMS and MD-BMED
power meters support the following commands:
Table 23: Supported Modbus Commands.
Command Name
Command Number
(Hex)
Description
Read Holding Registers
03
Used to read the data values from the power
meter.
Write Single Register
06
Used to write a single holding register to an
MD-BMS or MD-BMED power meter.
Report Slave ID
11
Used to read information from the identified
power meter.
The following guidelines are used for these Modbus commands:
●
All values are hexadecimal; spaces are not included.
●
The address is the value of the address switch on the power meter. This must be
different for each power meter on a single Modbus network.
●
The register’s high-order and low-order bits are the 16-bit value of a single, or first
register to be accessed for a read or write.
●
The CRC is the 16-bit CRC value. Note that the CRC’s LSB and MSB are reversed
in comparison to those for the registers and data.