Measurement Registers (M850 3X and duplicated 3X)

Internally, the M850 3X registers are duplicated in the 4X register area from address 41001, (internal register offset 2001 (07D1h)).
This allows PLCs that can’t read floating point data in the 3X area to retrieve the measurements from the 4X area.

The registers are listed with their Modbus addresses.
The data held at these addresses are Read-Only.
3X registers are read using function 04h.
4X registers are read using function 03h.

A sample read packet using code 4 to access the 3X registers will look like this:-
[Node][04][start address][No. of Double Registers Requested][CRC(2 bytes)]
e.g. To read line to neutral voltages on node 23h:-
[23h][04h][0006h][0006h(3, 4 byte regs)] [CRC(2 bytes)]
The node’s return packet will look like:-
[23h][04h][0Ch][12 bytes of data = 3 floating point numbers] [CRC(2 bytes)]

A sample read packet using code 3 to access the 4X registers will look like this:-
[Node][03][start address][No. of Double Registers Requested][CRC(2 bytes)]
e.g. To read line to line voltages on node 23h using the duplicated measurements in the 4X area:-
[23h][03h][07D0h][0006h(3, 4 byte regs)] [CRC(2 bytes)]
The node’s return packet will look like:-
[23h][03h][0Ch][12 bytes of data = 3 floating point numbers] [CRC(2 bytes)]

The list below is the default order of the 3X registers in the M850.
The order can be altered using the System Monitor program, supplied on request or downloaded from our website www.multitek-ltd.com, or by a suitable SCADA program.

Sample Coding