>Hello friends,
>
>currently i'm entering the wonderful world of PIC. For the beginning,
>i just want to start with a simple '84 programmer and a proto-board.
>Now ZIF sockets for 18 pins are very difficult to get and they are very
>expensive. So i want to use a in circuit programmer using the serial
>mode. From the archive i got some advices, to disable the oscillator (in
>my case a 4Mhz crystal) and to set a resitor between Vdd and Vpp.

Gerrit,

I beleive I was the person responsible for both the above recommendations.
You only need to "kill" the oscillator if there is a big >10mS delay from
the time Vdd rises to the time Vpp rises. The resistor between Vpp and Vdd
instead of a diode is only to allow for ESD that can (and has) built up on
the Vpp pin and caused the chip to scramble the EEPROM. Most people still
use the diode with good results. ESD is not allows big problem but if you
process the PCB further with spray-on lacquers and stuff, this is when
problems occur.


>
>Now to the difficult part: To aviod an additional power supply i want to
>use the design of a RS232-attached programmer. Has someone experience
>with this design and in circuit programming?

Hmmm. I have never seen a design where doing this has resulted in the 84
being programmed within the specs. No one I know of has shown how to get
both the Vpp voltage (13V) and the Vdd current (50mA) for the serial port at
the same time. Still, these programmers supposedly work even way out of
spec. But this is one thing I wont recommend.

Jim

P.S have a look at TELtronik. I thing they have a low cost '84 programmer.

http:/www.hway.net/teltro/tel_home