Navtel 9460 Protocol Analyzer info?

[Tony Duell]

> > Lots of fun, but I suppose a modern PC could do just as well,
> > presuming there's an app that's designed to capture and display
> > whatever goes by the serial port.
> 
> I can't remember what the software I used was called, but I think I still
> have it somewhere and  can check.  It came with a special double-headed
> cable though, and unless that cable was just a simple Y-split, I don't
> know if making one from scratch would be feasible.

These programs tend to need a PC with 2 serial ports. You want to monitor 
the data flowing over the 2 data lines in then link between the 2 devices 
you're investigating, so you need 2 serial inputs on the monitoring 
device (== PC). Typically you link the TxD line of the cable between the 
2 devices to the RxD line of one of the serial ports, and the RxD line of 
the cable to the RxD line of the other serial port.

Handshake lines are done similarly (if they're monitored at all). For 
example, the CTS line of one of the serial ports could monitor the RTS 
line of the cable, the CTS line of the other port could monitor the CTS 
line of the cable.

You don't use the output lines on the PC serial ports at all.

I seem to remember there was a project in Elektor magazine some years ago 
to make such a cable, which worked with one of the 'stnadard' monitoring 
programs. Don't ask me which progrma or to find the article, though.

-tony