ruby krishna

mc9s12 wake up problem

Discussion created by ruby krishna on Feb 22, 2012
Latest reply on Feb 22, 2012 by kef

Hi all,

       I'm stuck with a problem! please help me. We are using freescale mc9s12 microcontroller  for our automotive unit. Our ECU is consuming more power owing to sleep problem. Our only interrupt to the ECU is CAN.


I have studied the documents related to MSCAN thoroughly.i followed these steps for MSCAN sleep and wake up


1.set the slp request bit in the canctlo register

2. wait for acknowledgement from the canctl1 register( wake up enable) (MSCAN will go to sleep mode)

3. set the wupe bit canrier register and the wake up bit in canctlo register

4.clear the ccr register (s and i bit)

5. enter the stop mode


But the problem is, whenever i  set the slprq bit, slpak is acknowledged. MSCAN enters sleep mode immediately and gets in to intitalization mode.


I cant able to proceed further owing to this problem. Why it gets into initilization mode?? when i put the sleep request bit??...... please help me out.... I'm running out of time.