8048 programs first time then fails on subsequent attempts

Hi All!,

I’m a new 8048 owner and ran into a problem where I could program a 12F675 once using PicProg2006 v2.2.0.0 and the pic would work fine. Then I would try to program it again and it wiped the PIC and lost the OSCCAL value. The PIC was now unusable.

I found the solution in the following discussion:

It seems that if you are using the internal PIC oscillator which I am with the 12F675, you MUST HAVE the MCLR pin enabled when you program the PIC. If you leave it disabled, you can program it once, then it wipes on the next attempt.

Here is the part from the discussion that gave me the hint. I’m sure this was somewhere else in the PIC docs, but I missed it.

Hello Nitro,
You say you can programme OK the first time but after that is when the problem starts.
Forget problems with static etc, it sounds to me like you are programming using the internal oscillator and MCLR pin disabled (internal reset) With IC-Prog and a JDM programmer you will have problems when programming a chip that has been previously programmed with this config.
It’s a well documented problem and I have also experienced it and eventually made a different programmer to use on the 12F675 I had problems with.
If the chip was previously programmed with int osc and MCLR disabled you must bring the programming voltage up first before the supply voltage. The JDM programmer can’t do that. As soon as you plug your chip in it will have volts via the serial port and an internal clock so away it goes, never getting in to programme mode.


My JDM programmer has this problem, as well as my 8408. From the other comments on the thread above, it sounds like this affects non-12F675’s as well. Many thanks to David over at PicBasic. My apologies if this solution is already posted on the Velleman forum.

Happy Programming!


Please have also a look into related topics [url]K8048: Reprogramming not possible, possible solution] and [url]Programming the PIC16F627A for a 2nd time] for maybe another solution.