t-mac can connect to and read registers from devices which support the MODBUS RTU (Remote terminal unit) protocol.
MODBUS is a standard serial communications protocol and is the most commonly available means of connecting industrial electronic devices. MODBUS communication is via the RS-485 port and the protocol allows more than one MODBUS device to be connected to the same port.
The t-mac RS-232 port can be used instead of RS-485, as long as a RS-485 to RS-232 converter is placed between the MODBUS devices and the t-mac.