Something so wired has happened to me. I have built an experiment board for AT89S52. The setting of capacitor and resistor for reset circuit are 4.7uF and 10k, respectively. When I changed the oscillator from 12MHZ to 22.1184MHZ, the voltage at Pin 18 and Pin 19 are 5.0V and 0.0V (should be 2.33v and 2.13V around) and the MUC stopped running. What is the possible problem? I think the setting of capacitor and resistor for 22.1184 MHZ are wrong. Would you give me any clues?