hi~!

The pin "ALE/!PROG" of a 89C52, while the mpu is working, will output 1/6 crystal frequency pulses.
A LED is connected to that pin so that I can see if the MPU is working fine.

There are two DC motors on my soccer robot. I am testing it. But the MPU "failed" after some movements(within 1 minute). "ALE/!PROG" stop output pulses.

I removed the MPU and the driver parts and test them. Everytime I put the motors near the MPU, the MPU failed.


The DC motors and the MPU's batteries are separated:
motors: 6V acid lead battery;
MPU & sensors: SONY InfoLithium 7.2V (with 7805).

I can't find out any strange pulses or noise on the reset, Vcc and Vss pin, with the help of a oscilloscope.

Can anyone predict where the problem is?

thx
Stanley