Hi, yes we do this since years.
We use the Rx, Tx (Pin 5,6,7) at DP610 and DP610TM.
We drive 3 RS232 slaves by swithing with my switch-box.
printer, logger, in/out-device
I also wrote a printer-driver to print in 12 languages all characters you want, graphically.
btw: Tx-ready is not valid, is allways True.
DP610TM: There have to be an RX input level Otherwise you can't send TX-messages.