Help: USB to RS232 - How to test?

How do I determine if the USB port is actually getting data to/from the system’s COM port?

Some info:

  • I purchased a Generic USB to RS232 adapter based on a PL2303 chip.
  • I have installed drivers on both Vista Home Premium and Win XP SP3.
  • The driver that came with the adapter seems to have installed properly. There are no indicated errors. They appear to be Prolific drivers.
  • I have RealTerm installed.
  • I jumpered Tx to Rx plus other pins on the male DB9 connector.
  • I sought help from Prolific (re PL2303), but found nothing helpful.

But I don’t know how to look for data passing through the adapter. What I type on the keyboard does not show up on the RealTerm screen, but the Tx indicator in RealTerm flashes. Rx does not flash.
I am stumped, and about to cut the vinyl covers of the adapter.

I guess I should ask…would I see the other RS232 lines (CTS,DCD, etc) change if they were jumpered? I mean, are the states of these lines passed through the USB port?