CET PMC-D721MD, User Manual, Page: 19 / 27

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Chapter 5 Modbus Register Map
This chapter provides a complete description of the Modbus register map ( Protocol Versions 1.0 and
above) for the PMC-D721MD Digital Multifunction Meter to facilitate the development of 3
rd
party
communications driver for accessing information on the PMC-D721MD.
The PMC-D721MD supports the following Modbus functions:
1) Read Holding Registers (Function Code 0x03)
2) Force Single Coil (Function Code 0x05)
3) Preset Multiple Registers (Function Code 0x10)
The following table provides a description of the different data formats used for the Modbus registers.
The PMC-D721MD uses the Big Endian byte ordering system.
Format Description
UINT16/INT16 Unsigned/Signed 16-bit Integer
UINT32/INT32 Unsigned/Signed 32-bit Integer
Float
IEEE 754 32-bit
Single Precision Floating Point Number
For a complete Modbus Protocol Specification, please visit www.modbus.org .
5.1 Basic Measurements
Register Property Description Format Scale Unit
0000 RO U Float x1 V
0002 RO I Float x1 A
0004 RO kW Float x1 W
0006-0029 RO Reserved
0030 RO DI Status UINT16
0031 RO Reserved
0032 RO SOE Pointer UINT32
0034-0039 RO Reserved
0040 RO kWh Import INT32 x0.01 kWh
0042 RO kWh Export INT32 x0.01 kWh
Table 5-1 Basic Measurements
Notes:
1) For the DI Status register, the bit values of B0 and B1 represent the states of DI1 and DI2,
respectively, with “1” meaning active (closed) and “0” meaning inactive (open).
2) The range of the SOE Pointer is between 0 and 0xFFFFFFFF and it is incremented by one for every
new log generated and will roll over to 0 if its current value is 0xFFFFFFFF. A value of zero
indicates that the SOE does not contain any Log. If a
SOE CLR is performed from the front panel
or via communications, the SOE Pointer will be reset to zero and then immediately incremented
by one with a new ”Setup Changes via Front Panel” or “Setup Changes via Communications” event.
Therefore, any 3
rd
party software should assume that a SOE CLR E action has been performed if it
sees the SOE Pointer rolling over to one or to a value that is smaller than its own pointer. In this
case, the new SOE Pointer also indicates the number of events in the SOE Log if it is less than 32.
Otherwise, there will always be 32 events in the SOE Log.
5.2 SOE Log
The SOE Log Pointer points to the register address within the SOE Log where the next event will be
stored. The following formula is used to determine the register address of the most recent SOE event
referenced by the SOE Log Pointer value:
Register Address = 10000 + Modulo(SOE Log Pointer-1/32)*8
Register Property Description Format
10000~10007 RO Event 1 See
Table 5-3 SOE Log
10008~10015 RO Event 2