Quantum PLC and Modbus 2x registers

Any Quantum/Modbus "experts" out there know how I can read 2x and 1x registers via Modbus TCP/IP? I have a Quantum PLC and Unity Pro software. There is an existing Modbus network with Advantys I/O and ABB starters. I need to to read some status at bits level. Any ideas/help greatly appreciated.

Hi Pauly, sorry not a Modicon expert, but you need to use the appropriate functions, for the Register number, and they don't match, but that I mean...
Function 01 reads Coil Status bits, addresses start with 0
Function 02 reads Input Status bits, addresses starting with 1

Then, the next question will be, do those slave devices you mention support those function codes, or will you have to use the register commands to get the data then check the bits after the transfer?

Hi Pauly, I am not Modicon expert as well, but as I know Quantum PLC cannot read bit, it can read register only.

For Advantys I/O i think it will be Okay but for ABB starter if they give you the bit address it will be impossible to read from Quantum PLC

If the bits are gathered into a single 16-bit word (a 4x register in Modbus), Unity software includes BIT->WORD and a WORD->BIT functions. 984LL (the classic Modicon language) used BLKM (block move) to move a 4X register into and out of 16 consecutive 0x 'coils'.

I stilled got confusied. In the concept Quantum PLC, you can access to any State-RAM register (0x,1x,3x,4x) throgh ModBus RTU or ModBus TCP.

Is it true that you can only access 1x (%Mx) and 4x (%MWx) registers in Unity Quantum?

On Unity PLC's you use %M and %MW addresses to bits and integer variables. %M0 is Modbuss address 000001 and %MW0 is modbus 400001.

You can use/read modbus addresses 1x and 3x also ex. from scada, but this only gives you reading access to variables %Mx and %MWx.

So Unity differs from Concept, were you can read state of discrete inputs directly via modbuss addresses 1x and analog inputs via registers 3x.

On unity you have to copy discrete input bits allways to %Mx variables and analog inputs to %MWx registers first (IO mapping). After that, you can read inputs state/value via modbus commands...

Thanks Lare. That explains a lot! I guess they just tried to make the Quantum has the same behavior as the Premium and M340, where you can only access %Mx and %MWx registers through Modbus message.

I wroted it little bit wrong before. Concept PLC's uses little bit differently memory addresses for inputs than Unity PLC's. (Memory allocation)

What I meanet was that on Schneider's Concept you can use 3x addresses to also read analog inputs directly, not only read access to word variables.
(Because on Concept PLC's analog inputs are linked automatically to 3x addresses and discrete inputs to 1x addresses, ex first analog input can be on Concept 300001 modbus. So, if you read modbus address 300001 on Concept PLC, you will see analog input's raw data on this address...

This depends of how many analog inputs you have, if you have ex 10 analog inputs => memory area 300001-300010 is reserved for analog inputs (user can chance this memory area from parameters). Memory area above this can used for variables, and if you ex. read modbus address 300100 on concept you now see value of variable which have modbus address 300100 or 400100.

On Unity PLC's inputs aren't automatically linked to modbus addresses => Whole momery area 3x / 4x is used for variables only. Same thing also for 0x/1x addresses.

So if you try read ex. 300001 address on Unity, you won't see first's analog input raw data, you will instead see value of first memory word, which is %MW0.