XXXUSB485S = TRPC08S will work with a HART modem 

This is a 2 dual com port converter with terminal connections for RS485 and a D9 plug for RS232. This is very important as the DTR in the D9 connection for RS232 provides power for the HART modem

XXXUSB485 = TRP-C08 will not work with a HART modem 

The terminal connections are restricted to Rx, TX, RTS and CTS.