PIC16f877A first 8 bytes destroyed after closing PicKit2 programmer app....

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Hello to the forum,

Using PicKit2 i write/verify a hex file on 16F877A , all ok.

I even load another file and back read the 877A and all still ok.

BUT then i close the pickit application,
when i re-open Pickit application and read the 877A the first 8 bytes are FF , the rest bytes are proper.

My program has nothing to do with on-the-fly code-programming to overwrite the first 8 program memory bytes ...

The program is (now only a simple port-toggle , problem is still happening ...)


OPTION_REG.7 = 0 ; ENABLE PORTB PULLUPS

LOOP:
portb.0 = not portb.0
GOTO LOOP

Hello LakisFM1,
Welcome to the forum !
I have some thoughts, which manifest as questions.
Here goes . . .
Are you compiling this code using PBP and MCS ?
If so, Make sure to choose, " Compile " and Not, " ICD Compile " There is a world of difference in the hex output between these. As I usually do not use the ICD, I have unchecked it's selection in the toolbar settings, so as to avoid tripping myself.
EDIT: Anyway here is your code working for me

DEFINE OSC 4
TRISB = 0
OPTION_REG.7 = 0 ; ENABLE PORTB PULLUPS

LOOP:
portb.0 = NOT portb.0
PAUSE 500
GOTO LOOP