Don\'t bother with getty: that\'s what you\'d run if you wanted to let a terminal login to the Z.
I think there are some instructions on the serialio.com site for setting up tyhe serial port. Some ROMs default to starting a getty on it, and the website tells you how to shut that off. But read the Z\'s menu carefully: the options on the Sharp 3.10 ROM are different from the one on the webpage I read (not serial.com\'s), so blindly following the instructions for which key to press might not work.
Ran