Re: MPC555 Temperature Sensitivity?

Randy,

The problem turned out to be the interface to external RAM. We needed 
to add wait states to account for some temperature effects in the 
access time to RAM, and that has solved our problem. We did have some 
floating pins, but not the critical ones in your list.

Thanks for your input, in any case.

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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