Hi,

I am using a 750-842 FBC to communicate with several other devices on a Modbus TCP network setup. I have a 352 Remote I/O, 2 Power Monitors through a Gateway, and a Generator controller.

For some registers within the Power Monitors, The floating point value occupies 2 consecutive registers (i.e. 4002, 4003).

How can I combine these two so that I can read the value? Im using the Ethernet_Modbusmaster_TCP function block to retrieve data from each of these devices.

Thanks in advance,

Jason

You can try something like:

VAR
  awWords      : ARRAY[1..2] OF WORD;
  pReal : POINTER TO REAL;
  rReal : REAL;
END_VAR
awWords[1] := (* whatever code is needed to read the register *);
awWords[2] := (* whatever code is needed to read the register *);
pReal := ADR(awWords);
rReal := pReal^;

AT. Below are examples where the head address of the array is mapped to individual address for float variables.

HOLD_REG AT %MW0: ARRAY[0..20] OF WORD;

POS_X AT %ML0 : LREAL;
POS_Y AT %ML1 : LREAL;
POS_Z AT %ML2 : LREAL;
POS_S AT %ML3 : LREAL;

http://forum.codesys.com/viewtopic.php?f=2&t=5045

%ML0 does not exist.
if the float is same as real in definition you only have to do a dword_to_real