Hi Israel,

You are absolutely correct, you CAN re-program the 16F84 in-circuit.

All you have to do is provide a means of connecting at least four of the
16F84's pins to your programmer. If your circuit can provide power,then
this is all you need. If your programmer needs to provide power,then you
need to run a wire for a fifth pin,too.

Another consideration is that the programming connections cannot interfere
with the circuit's operation and vice versa. Usually this means that you
will need to place a small resistor (a few K ohms) between three of the
PIC's pins and the rest of the circuit. You then connect the programmer
directly to the pin,and the resistor isolates the circuit. In some cases,it
is also necessary to short the two oscillator pins together to prevent
oscillator startup.

There is probably an App Note on this,but I don't know. Maybe someone else
can help?

Sean

At 09:53 AM 9/5/99 -0700, you wrote:
>Hello,
>
>I am fairly new to the pic family of controllers and have a question.
>Can i program the 16f84-04p in-circuit?
>It is very important in my current app (micro-sized robot) to be able to
program and debug
>while the chip is in.  I hear lots of talk about removing the chip and
inserting in a
>programmer. I cannot do that every time i need to tweek some code.
>Am i way off?  Do i need a differant chip?  Thank you for any help.
>
>Israel

|
| Sean Breheny
| Amateur Radio Callsign: KA3YXM
| Electrical Engineering Student
\--------------=----------------
Save lives, please look at http://www.all.org
Personal page: http://www.people.cornell.edu/pages/shb7
mailto:shb7@cornell.edu ICQ #: 3329174