Exception handling on mpc8xx cores

Mark Chambers markc at mail.com
Thu Dec 9 00:06:56 EST 2004

> On Wed, 2004-12-08 at 05:15, Robin Gilks wrote:
> > Greetings
> > 
> > Any Freescale lurkers out there?
> > 
> > The mpc866 manual implies that if the internal core times out an 
> > external Transfer Acknowledge bus signal (by exerting the internally 
> > generated Transfer Error Acknowledge signal) an exception is generated.
> > 
> > I've tried extending the external TA signal well beyond 2040 clock 
> > cycles the maximum timeout allows and I see the busses start up again 
> > (indicationg that they are no longer waiting) but I don't see anything 
> > on TEA and I don't get an exception thrown.
> > 
> > Any clues? Manual error?, silicon error?, my brain error?
> Did you enable the bus monitor in the SYPCR register?

You've also got to have ME set in MSR to get the exception.  For whatever 
it's worth, I have an mpc852 design (part of 866 family) that uses external
acknowledge and it works as advertised.  I've seen the acknowledger,
a DSP, fail, and we get a machine check exception.  (I've never 
looked at TEA, though).

Mark Chambers

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