TclTerm, which is part of MakeItC and BASICtools, now has a pulldown menu to
wiggle the control lines out of the FTDI USB connection.
This can be helpful in the debug of the USB connection or the CPU.
So with a multimeter you can see toggles of RESET (DTR) or BOOT (RTS)
Or send a bunch of characters out on RXD (also visible on a multimeter)
You can also see if the CPU is alive, by setting the BOOT pin low, then toggling
RESET, and then typing a ? to send to the CPU. If alive, the CPU responds with
Synchronized.
These files (stand alone executable or Tcl file included by MakeItC and
BASICtools) are in the Files section of the Forum.