Modbus communication.

Hey guys ,
I am in a bit of confusion regarding modbus communication.I have MLX 1200 which uses its channel 0 port as a "RTU master" and is connected to a 1761-net AIC module at (8 pin RS 232 port), it then uses its RS485 port to communicate with drives.

Next I have a MLX 1400 controller , which also is configured as RTU master but doesnt use a NET AIC module to communicate with devices on RS 485 network.

As per my understanding NET AIC module is used to convert a RS232 signal to RS485 , if so then how come MLX 1400 is able to communicate without NET AIC??, where as both controllers are configured as RTU master..

Pls help

http://literature.rockwellautomation.com/idc/groups/literature/documents/um/1762-um001_-en-p.pdf
"The MicroLogix 1200 can be connected to a personal computer. It can also be
connected to a DH-485 network, or a Modbus network as an RTU Master or
RTU Slave using an Advanced Interface Converter (catalog number
1761-NET-AIC)."

https://ab.rockwellautomation.com/Programmable-Controllers/MicroLogix-1400
"Two serial ports with DF1, DH-485, Modbus RTU, DNP3 and ASCII protocol support"

The 1400 has built in protocol support for Modbus RTU, 1200 needs the 1761-net AIC module for Modbus RTU protocol support.

Regards,