RE: MPC555 bug

Take a look at CLKOUT as it is a good indication as to wether or not the
PLL has locked.  You can have reset problems if you have a bad clock
input depending on MODCLK settings.

Also look at some of the archive mails which discuss reducing the value
of the HRESET pull-up to 1K.  Mke sure nothing is external to the CPU is
pulling HRESET or SRESET low i.e. try removing the BDM connector.

Regards,
Allan

-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf
Of bclairc (sent by Nabble.com)
Sent: Tuesday, January 10, 2006 7:23 AM
To: [email protected]
Subject: [MPC500] MPC555 bug



Hi,

I have got a strange phenomenon on a board and i have searching for days
without solutions; this board is not new (exists for 2 years) and the
problem is appeared 3 weeks ago. At the power up of the board, it could
occurs (statistic is around 1 for 500 power up) that several outputs of
the MPC are tied to 0V and stay at this level.  In particular all GPCM
outputs which occur conflicts, or TouCAN outputs which become dominant.
In this case, HRESET is kept to 0V without effect. I have tried to
activate the PORESET but without success. I have tried to cut VDDL,
VVDI, VDDSYN, KAPWR but when i put them back the problem is still there.

I have cut all previous supplies plus VVDH and VVDA : same results. The
only supply i had not cut is VDDSRAM....

The only way to exit from this position is to cut all supplies of my
board !

 I have thought of a possible latch up phenomenon but do not understand
why it occurs now, after several monthes of good working. The board
design is still the same. Could I have an internal MPC problem which can
exist with these results ?

Thanks for your help,

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