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MC33908 WkUpSrc register read always returns 0.

Question asked by Bhanu Kandimalla on Feb 10, 2017
Latest reply on Feb 13, 2017 by Bhanu Kandimalla

We are using MPC 5643 with MC33908L(SBC). After intializing the SBC and SPI, I am trying to read the SBC's wake up src register where one of the IO_0 is setup as wkup src. The IO_0 is configured as rising edge wakeup detection. (Init IO_WU1 is properly set as x00040. So after intializing, All the read SPI command to the SBC are successful. But the WkUpSrc read is always returning 0. The SBC deglitch time seems to be 70us. The switch that drives the IO_0(from 0 to 24v) has a 1uF Cap. When the switch is turned out, I expect the wakeup Src register to be set for IO_0. But SBC is returning 0. Any idea what is going wrong here. Thanks in advance!!