Jarod Stone

S12X PLL, RTI, Timer Prescaler Problems

Discussion created by Jarod Stone on Apr 25, 2006
Latest reply on Apr 26, 2006 by Jarod Stone
Dear all,
I'm trying to move a small application from an S12 to an S12X and I'm having a few problems. First of all I want it to run at 40MHz bus speed so I've set the PLL to 80MHz compared to the S12 which used to run from a 16MHz crystal without PLL. From here the problems started... I tried to set the RTI interval at 512us (0x44) and I don't know if that's correct or if it's working. Next I'm having problems with the timer prescaler. How do I set the prescaler for 1us ? And last, I've noticed that the PWM is acting a little weird. I have a buzzer on my board and i set the pwm frequency to 1953 Hz on both MCUs. However, on the S12 I can hear the buzzer very loud compared to the S12X at the same volume setting. And the volume goes lower as i increase the PLL freq. or higher as i decrease it. The same happends with a motor which is controlled by the MCU. On the S12 i get a lot of power from the motor and on the S12X it is running very "soft".
Any help is greatly appreciated.