Hi Jon, I use in circuit programming only, even with DIP packaged PICs. I hate to extract/insert the chip milion times (16F84s are ideal for this, does not even need UV erase). You have to think about ICSP during the circuit desing though. I use following setup: VDD and GND connected directly to programming header, MCLR connected to header and thru 39K resistor to VDD, RB6 & RB7 connected to header. The last two pins can be used as outputs in my design, since my programmer tristates its clock and data lines when the PIC is not in programming mode (I am not familiar with other programmes, mine is a home-brewed one). There is a slide swith in the programmer for +5V, so VDD can be supplied either from the circuit or from the programmer. There are several drawbacks in this approach. Nothing can be connected to the MCLR pin, which does not withstand 13V, RB6 & 7 are limited to output use only, the circuits connected to them have to tolerate the pulses during programming (usually not a problem) and should not draw excess current (like 20 mA LED or optocoupler). You may also run into difficulties, when verifying the PIC at different voltages (my programmer does not support this). If your circuit can supply some 20-40 mA to the VDD pin during programming, you need not to connect VDD to the header at all. Connect only GND, RB6, RB7 and MCLR instead of VDD. Josef > However, space is very limited, so I want to use the surface-mount version > of the chip. I plan on programming them in circuit, and will provide a > four-pin header for each chip on the board. I plan on using RB6 & RB7 only > for programming, and so will not need to isolate them from the circuit > (since they will only go to the pins on the header). ====================================================================== Electronical devices for chemical laboratory, custom electonics design ---------------------------------------------------------------------- Snail Instruments Josef Hanzal Vojanova 615 phone/fax: +420-311-24433 266 01 Beroun e-mail: euroclass@pha.pvtnet.cz Czech Republic URL: http://www.vitrum.cz/snail/ ======================================================================