I want to know for A-B PLC with Modbus RTU and Modbus over IP, what are my options .. I am using in-rack Prosoft modules for SLC and Controllogix but I still have to edit codes to manually map individual bits and bytes to modbus registers and this pratice is time-consuming. I don't know if is there any other solutions that more transparent and let me map all data with minimum work...

To begin with, I don't know of any "direct mapped" solutions...ones where you won't have to write your own explicit data transfer commands.

That being said, the Prosoft solution is more trouble than it's worth because you have to write the mapping file for the Prosoft module in addition to the PLC code. For that, there are 3 options:

1. On ControlLogix, AB has code on their site for implementing Modbus/RTU directly via the CH0 serial port. It's a bit complicated mostly because it's ladder logic, but it's not too bad beyond that.

2. Some of the Micrologix PLC's implement Modbus directly as their native remote I/O protocol...they actually don't support ANY AB protocols for remote I/O. AB did this intentionally to try to force you to buy a more expensive processor (such as a CompactLogix) rather than doing everything with Micrologix. At least the Micrologix 1100 costs less than most of the I/O, so I'm finding myself installing them as "smart I/O" frequently for the cost reduction, not because I actually need another PLC.

3. A Digi One IAP doesn't require the mapping that the Prosoft module requires. You have to go through some funky "address gymnastics" but essentially you can just use the appropriate MSG instruction to get the location you want. Digi distributes spreadsheets to make this easy. I have actually implemented this solution using Acromag Modbus/TCP modules. It actually works extremely well in practice. There is a single Digi One module sitting on an Ethernet cable beside the PLC. It allows the PLC-5 to implement Ethernet-based remote I/O. Each IAP module can map up to 16 addresses (x.x.x.0-15). It can do more but when you attempt to map a ControlLogix backplane (this is how it actually looks to the PLC-5), RS-Logix is "too smart" and won't let you use slot numbers larger than 15.