Re: MPC555 Temperature Sensitivity?

Hi Randy,

Thanks for the quick reply. We definitely have pins that are not
pulled up externally. I have two follow-up questions:

1) Would this explanation be consisent with the fact that the problem
seems to go away when we've got our BDM connected and all code and
data is in external RAM with internal flash disabled?

2) We have two slightly different board layouts. We happen to have "C"
temperature (-40 to +85C) processors on one rev and "M" temperature
(-40 to +125) processors on the other rev. So far, all of the problems
have been on the later rev board which has the "M" processors. We have
no problems with the earlier rev board with "C" processors. Does it
make any sense to you that we would have more temperature sensitivity
with the "M" processors, which are actually rated to a higher temp?

We're not raising the temperature much in our tests. In fact, we have
found that temperature rise from having direct sun on the board is
enough to cause the problem. The problem goes away if we close the
blinds and comes back as soon we open them and have direct sun on the
processor.

Joe

--- In [email protected], "Dees Randy-rsaf30" <randy.dees@...> wrote:
>
> you probably have floating pins. revision M fixes an errata that some of
> the internal "weak" pullups were not actually disabled when you disable
> (SPRDS) them in the PDMCR register. Now that they are always disabled
> when you disable them. The MPC555 Reference Manual states that these
> pins must have external pull ups. The weak pull ups are not strong
> enough to be relied on in a system over temperature.
>  
> BG, BB, BR, are the primary pins that cause issues in customers targets,
> but bi_b_sts_b, burst_b, bdip_b, ta_b, ts_b, tsiz1, tsiz0, tea_b,
> rd_wr_b, br_b_vf1_iwp2, bg_b_vf0_iwp0, bb_b_vf2_iwp3 are all of the pins
> that that the pull ups are now really disabled by SPRDS (like they were
> supposed to be).
>  
> randy
>  
> 
> 	-----Original Message-----
> 	From: [email protected] [mailto:[email protected]] On
> Behalf Of trailrunner23
> 	
> 	
> 
> 	Hello All,
> 	
> 	I asked a question recently about problems we're having, and I
> have
> 	more information. We have two different MPC555 part numbers:
> 	
> 	MPC555LFMZP40 (-40 to +125)
> 	MPC555LFCZP40 (-40 to +85)
> 	
> 	Both of these are "K3" parts (IMMR = 0x3032).
> 	
> 	The problem we're having is that our boards with M parts are
> getting
> 	Machine Check Exceptions when our enclosure gets warm, but we're
> 	talking about 50-55C, nowhere near the ratings, and it seems to
> be a
> 	problem on the M parts, which are supposed to tolerate very high
> 	temperatures.
> 
> 	.
> 	
> <http://geo.yahoo.com/serv?s=97359714&grpId=6276387&grpspId=1601554205&m
> sgId=3638&stime=1150858009> 
> 	 
> 
> 
> 
> [Non-text portions of this message have been removed]
>







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