I am trying to receive parameters from an APB PLC installed in a compressor. The process is locally controlled from the PLC. Just need to view some parameters like pressure and temperature which are stored in the internal register of the PLC.

The vendor has provided register address of the form:
4818H
481AH
481EH etc

Can I directly input this sort of address in the configuration window while configuring SCADA points?

 

DCS documentation is available only to the privileged few, which doesn't include me, so I can only give a generic Modbus answer.

The fact that the PLC has register addresses means it is the Modbus slave. So the DCS has to be the Modbus master.

The PLC register addresses, in hexadecimal, start with the numeral 4. The first digit is probably not a 'leading numeral' 4 that is supposed to tell us that the registers are holding registers, addressed with Modbus function code 03. The leading numeral 4 is probably part of the register address (4818h is decimal 18456) because of the range that the values fall in.

But there's strong likelihood that the data is in holding registers.

What isn't stated is what the data format is in the PLC registers.

One might guess that since the first two registers, 4818 and 481A, are separated by 4819 that the data occupies two successive registers, like a long, 32 bit integer or a 32 bit floating point. But, that's a guess based on the limited information provided. You might inquire what the data format is in those registers. Otherwise, you experiment. Modbus tends to be an empirical protocol.

Then there's the dreaded one offset where the true register address depends on whether the registers are numbered from zero or from one. If the registers are hex, there's a slightly increased chance that the registers are numbered from zero, because those who talk hex tend to start counting at zero.