Reset MPC8245 Twice

[___2015]

Our company has beening using MPC8245 for a very long time. Long before I join it. One phenomenon here seems to be very common, which is that the MPC8245 has to reset twice when powered up. Let me explain.

For a embeded system, reset signal is fatal, and everything system has to be reset when powered up. Yes, but only once. However, when using the MPC8245, we find that if we only reset the MPC8245 once, the system will not act normal. specifically, not program is running. Looks like the MPC8245 is not ready yet. And if we reset the system twice, it will work like a charm everytime.

Although we fix this bug, I still wonder if Freescale knows it. After I read the newest datasheet and the errata. No Freescale offical paper has never mention about, which makes me little nervous.

Is it a common phenomenon or there is something I got wrong? Has anybody faced this problem before?

[alexander_yakov]

There is definitely no official Freescale (now - NXP) requirement to assert reset twice.

Probably, this may be related to clock - reset may be released before clock become stable, so internal PLL gets confused.

Please try to prolong first reset assertion until all power supplies and input clock become stable and deassert it only after this.

Hope this will be helpful.

Have a great day,
Alexander

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