Perhaps I missed it in the thread, but the heart of the communication regardless of the higher level language is going to more than likely be MODBUS over RS485, or TCP, etc. You need a backbone communication to the entire system that allows for a multidrop addressable network.

It seems though that the original intent of the OP was "I want to replace PLC with microcontroller in conveyor belt application. " !
Which IMO would be a backward step.
Max.

 

My PLC experience is limited to looking over the shoulder of a co-worker who as programming one, but one very big feature that I saw which is not in any plain microcontroller that I'm aware of, is the programmable logic itself! AND gates, OR gates, etc.. With a PLC, at least the one he was using, you build the equivalent of actual low level logic circuits, and that is wrapped with a microcontroller. It was actually very cool and as soon as my request for the 25 hour day comes in I'm going to learn how to program one!

I hereby grant you the 25th hour (use the method I do...remove the battery from your wall clock).

Max's suggestion of Automation Direct is a good one.

On the other hand, if you are already into microcontrollers or linux, there are some software PLC controllers (such as OpenPLCProject) that you can use on hardware you may already have).

 

I played around with these IC's when they came out in the 70's interesting little chip.
The MC14500B Industrial Control Unit is a CMOS one-bit microprocessor designed by Motorola for simple control applications in 1977.
It is well-suited to the implementation of ladder logic, and thus could be used to replace relay systems and programmable logic controllers, also intended for serial data manipulation.
Max.

 

My background from embedded System. I have hands on experience with microcontroller. I am not familiar with PLC and it's programming. I do not want to learn PLC programming. I want to stay with Microcontroller.

I want to replace PLC with microcontroller in conveyor belt application.

For an example

My guess they are using PLC so Can I replace PLC with microcontroller for airport baggage handling system?

In practically, Is microcontroller suitable and efficient for this project as compare to PLC?

A PLC is fundamentally an enormous microcontroller. It does likewise things a microcontroller can do, however with higher speed, execution, and unwavering quality (now and then). A microcontroller is truly only a little low force CPU/PC with some yield registers wired to pins rather than different registers or gadgets
so PLC will go best

 

It is now 9 months, I would hazard a guess the OP has made a decision by now.
Max.

 

I say rip the Microprocessor out of your PLC. It doesn't need C for processing. Frank said, "Joe the machine quit working. The ladder logic no make machine language no more. Maybe we should put that chippy thing back in". Joe said, "Forget it frank I don't like no stinkin C programming". Joe said, "Frank you need to stop watching Treasure of the Sierra Madre. The line is you don't need no stinkin Badge". LoL I'm sorry, LoL stands for Laugh out Loud for all you ladder logic programmers.