In a message dated 97-03-17 11:40:53 EST, you write:

<<
 Hi all,

 I'm trying to program a 16C84 with a low cost PARALLAX programmer
 and have some trouble:
         1/ I'm obliged to program 3 or 5 times the chip to have
 the oscillator programmed for CRYSTAL and not RC
         2/ I have the programmed chip (SMD), then sold it onto the board.
 I connect RB6,RB7, MCLR and VCC to the programmer in order to modify
 the program. Problem is as the chip is programmed for Crystal oscillator
 the programmer as many difficulties to read and program it.

 Does anybody know if it's necessary the oscillator section run properly
 to re-program a 16C84 ?
 Does somebody have the same problem with a parallax programmer ?

 Regards,
         Philippe.
  >>

Philippe,
The system my company makes has 14 PIC16F84s on a single control board.  They
are all SMD chips and are all programmed through an in-circuit programming
connector.  I use the Parralax programmer to accomplish this.  I have
experienced the same type of problem that you describe here.  Our problem was
caused by the Ocsillator (We use one 10mhz oscilator to drive all 14 pics).
 The Microchip spec. say that there can be no oscillation on the crystal
inputs durring the first three transitions of the serial clock used for
programming.  We now put the oscillator in a socket and insert it after
programming is complete.  This seems to solve all of our little quirky
problems.
Hope this helps.
Dave Duley
V.P. DreiTek Inc.