I wrote:
> 2)  The debugger could feed individual instructions to the CPU core,
>     one at a time.  [...]  The Microchip PIC is reportedly capable of this
>     in a special test mode (with Vpp applied).

Tjaart van der Walt <tjaart@WASP.CO.ZA> replied:
> Hah! I hope you didn't think you'd get away without explaining this! ;) (=
> On the PIC)

I'd be delighted to share details, if only I had some.  When Vpp is applied,
the PICs have various test modes in addition to the documented programming
mode.  I'm not sure if even the ICE vendors get this information.

Eric