JDM issue solved?

Design Concepts
1

Last week I got a PIC16F877A which wasn’t programmable with my own JDM, although I burned a lot of ..A chips with this programmer before.

I noticed that the voltage at MCLR# was lower than on a “common” PIC16F877A. It didn’t help to vary the software settings of IC-Prog like IO-Delay or Interface type of IC-Prog, so I finally tried to increase vpp by using an external PSU - with success!

Maybe (or hopefully) this is the solution for everybody who wasn’t able to burn a PIC (especially the new …A and the PIC18F types) yet:

  • use either two 9V batteries or a PSU which delivers at least 15V. A regulator isn’t required, the zener diodes limit the voltage
  • don’t forget the 220 Ohm resistor - it limits the current and protects the circuit
  • plug the PIC directly into the JDM module socket when you burn it the first time, because an erased PIC requires the pull-down resistor at pin RB3 which disables the low-voltage programming mode.

Good luck!

Best Regards, Thorsten.

mbhp_jdm_vpp_fix.gif
mbhp_jdm_vpp_fix.gif501×307 11.7 KB

2

and what about the “pre-flight-check” ??

should i do it as on the site and get the same results ?

or is it different now ?

is the change good for all the other pics ?

3

This mod improves the MCLR# voltage, use it if the output voltage of your COM port is not high enough.

The checks are still the same.

The results are “improved”.

The derivative doesn’t matter here.

Just try it with an external supply if your JDM doesn’t work (with a certain PIC or with any PIC)

Best Regards, Thorsten.

4

Thats great that you were able to solve this problem Thorsten! ;D