> As usual I have this problem ... I haven't seen anything written about
> serial in-circuit programming of the 16LC84, aside from the little bit in
> the data book on page 52.  I hadn't paid much attention to it until
> recently; that is, now that I know I have to use an SOIC package device in
> the final product design.

In-circuit programming is wonderful, if you are aware of its constraints.

> I see in-circuit programming to be very advantageous, since it will allow us
> to load a routine for hardware verification during manufacturing test, and
> then re-program the 16LC84 with the operating code ... all without
> disturbing the hardware.

Great for debugging (before and after production) too...

> Trouble is I can't find anything in my MPLAB or Picstart PLus manuals (or
> the Microchip CD) about considerations for in-circuit programming: neither
> how one should size the isolating resistors shown on page 52, nor the
> availablilty of a commercial serial programmer.  Is it one of those things
> that's "left as an exercise for the reader", or is there a product already
> available to do the job?

I don't know about commercial serial programmers; I know I've built two of
my own, and incorporated circuitry directly onto the boards for a couple
other products.  As for software, I'm afraid I don't know; my good stuff I
developed for work, and I don't know if I can give it away.

As for the isolation resistors, that really depends upon your application;
if you are using RB6 and RB7 for output only, you can skip the resistors
entirely (though you need to ensure that whatever they control won't "mind"
if these mins have signals on them during programming).  If they are inputs
only, the resistors can be large, subject only to the constraint that large
values may slow down the response of the port.  The final caveat to consider
is that if the PC is to be left connected you may want to have it wired so
as to be able to "tri-state" itself from those two pins or else use a relay
on your programmer to disconnect those pins entirely.

> Because of time constraints, I'd rather buy than build one, but building is
> still do-able.  Perhaps it's nothing more than building a driver/buffer
> stage between my Picstart and the application circuit?  Does anyone out
> there have any good pointers for in-cicuit programming?

I wouldn't be surprised if the PicStart could handle ISP'ing easily; I've
never done it.  One concern I'd have regarding your application, however,
is that I'd suggest if possible using RB6 and RB7 for outputs only (or else
for nothing at all) and putting moderately large (e.g. 47K) resistors in
series with the RB6 and RB7 wires.  Since you're using the LC part, it sounds
as if your voltage won't always be at a nice even +5; when programming, you
should have VDD at +5, but you should also verify your part at whatever volt-
age it will be running in the "real world".