Appendices
Appendix B - MD-BMS and MD-BMED Power Meters Modbus Absolute/Net Value Measurement Registers and
Protocol Commands
88
Building Technologies
125-202
06/06/2017
The response from the power meter at address 37. Two bytes were read from the
requested register, 000C. The value of the registers read was 0000. The DRC value
was 4070. The number of registers read must be between 1 and 125, inclusive.
The value sent as the register address in the read and write Modbus commands is
not the register listed in the table, instead an abbreviated version is sent. The actual
register address sent is the Modbus register value minus 40001. For example, the
address sent in the command message for register 40025 is actually 4061 (0FDD
hexadecimal).
Write Single Register
This command writes to a single holding register of the power meter. The normal
response is an ecno of the request, returned after the register contents are written.
Table 26: Format for Modbus Command 06.
Command Information
Command Layout
Example Command
Power meter address
nn
37
Command number
06
06
Register to write – high order bits
xx
00
Register to write – low order bits
xx
00
Register value to write – high order bits
xx
00
Register value to write – low order bits
xx
00
CRC low order bits
xx
8C
CRC high order bits
Xx
5C
Command Example
This command writes to a power meter with an address switch setting of 37 hex (55 in
decimal), writing one byte at register 000C, and writing a value of 00 to clear the KWH
registers. The data value of 0 is sent to register 0. Note that offset 0 corresponds to
Modbus register 40001. The CRC is 5C8C. All values are hexadecimal.
Table 27: Example for Modbus Command 06.
Example Request Field Name
Command
(Hex)
Response Field Name
Response
(Hex)
Power meter address
37
Power meter address
37
Command number
06
Command number
06
Register to write – high order bits
00
Register written to – high order bits
00
Register to write – low order bits
00
Register written to – low order bits
00
Register value to write – high order
bits
00
Register value written – high order
bits
00