Respected experts,

I was using AEC flash programmer for my mcu board with 89S8252 it was working perfectly but from few days it started giving message

Flash byte error in address 0000

After checking the all the cable connections and level with the simple logic prob I could not find any thing wrong. Then I assembled M. Asim Khan circuit it also didn’t worked it said

No response from the MCU

Even with ponyprog too the problem was same.

Now it led me to think that MCU had gone so I purchased the new MCU Not one but four even then It didn’t solved my problem by replacing. When ever I checked the MISO pin it remained always high it never showed a signal like flickering. On MOSI and SCK pins it showed flickering which I assume that these are working.

Why there is no output on MISO and how can I check it as I dont have CRO. Only I have a logic probe and a multimeter.

Please do help me come out of this

Regards…Manjeet