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Why clearing RTIF bit will cause PORF, LVRF bit cleared also for S12 MCU?

Question asked by dongpeng hou on Nov 17, 2014
Latest reply on Nov 19, 2014 by dongpeng hou

Hello, I found a strange problem on S12G also on S12XE MCU. In our bootloader code, it will clear the RTIF bit (CPMUFLG_RTIF on S12G, CRGFLG_RTIF on S12XE), but I found other bits in the register also were cleared. PORF is used for power on reset judgement in my code, it can't be scratched.


My code is below:

S12G128 MCU:

CPMUFLG_RTIF = 1   // after this code, PORF is cleared.


S12XE256 MCU

CRGFLG_RTIF = 1     // after this code, PORF is cleared.


But if the code is as below, the PORF bit was not affected.

CPMUFLG = ~(U8)CPMUFLG_PORF_MASK;        /* Clear CMPMU int flags - not needed but good practice */