hcs12, PLL to 25Mhz, fluctuation of power make problems to re-start :-(

[MarioA]

subjet: hcs12, PLL to 25Mhz, fluctuation of power make problems to re-start  

Hi!

I work and HCS12 DG128 with an external oscillator 5 Mhz and I configured the PLL to automatic lock at 50 Mhz, (the max high speed).

 

In normal conditions (source=5Volt ) my target start very well (25 MHz of bus speed) but my problem is in the fluctuation of the source of power

 

when fall more of 2.8 volts the CPU is dead ( is ok), and then..

when rising slowly on 3.2 volt until 5 volt  the CPU in some times don’t work ( is bad )

 

Note: To change the internal bus clock 25Mhz to 5Mhz avoid my problem but  I need work at 25 Mhz.

please, help me, and excuse my bad English.

 

 

best regards

[Lundin]

I might be wrong, but isn't the maximum frequency 40MHz?

I am however certain that DG128 does not support 3V operation and that Freescale only guarantees operation between 4.5V and 5.25V. Go outside those limits and the processor might behave randomly.

As suggested, you must have an external voltage supervisor.

[kef]

9S12DG128 doesn't have LVR (low voltage reset circuit). You should use external supervisor/brown out detector or upgrade to 9S12XD.