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Configuring System Registers
Modbus Absolute Address/BACnet Object Assignment
REGISTER TEMPLATE
Description 2601
PF Sign Convention 2248
V1 Multiplier 2203,2204
V2 Multiplier 2205,2206
Configurations
System
Description 31 Char
PF Sign Convention ANSI [1] or IEEE [2]
V1 Multiplier Any > 0 [1]
V2 Multiplier Any > 0 [1]
Modbus Protocol Commands
If configured for Modbus, the MD-xxHD networked power meter family follows the Modbus RTU protocol
and supports the following command set.
Supported Modbus Commands
Command Name
Command Number
(Hex)
Description
Read Holding Registers 03 Used to read the data values from the MD-xxHD meter
Write Single Register 06 Used to write a single holding register to a MD-xxHD meter
Write Multiple Registers 16 (0x10)
Used to write multiple registers (useful but not required for
32-bit values and strings)
Report Slave ID 17 (0x11) Used to read information from the identified MD-xxHD meter
Slave Address
For Modbus/TCP the base slave address (or “unit address” as the Modbus TCP spec. calls it) is fixed at 1.
See
the section “Serial Protocols” for additional information on setting the Slave Address and finding the
address of a specific meter element.
Modbus String Entry
Registers that are identified as “strings” are handled uniquely by the MD-xxHD power meter. Each
register in the string block must be written to sequentially without interruption either by using a
write
multiple command or by sending single register commands back to back. The final character in the string
MUST be a NUL character (ASCII 0). The meter will process the entire string only if these two conditions
are met, otherwise the data is ignored. This special processing has been implemented to protect partial
updates for network settings.