AnsweredAssumed Answered

Problems getting a blank QG into background mode

Question asked by David Payne on Nov 30, 2006
Latest reply on Sep 19, 2008 by David Payne
The QG, when blank, is very troublesome to get into active background mode.
I believe that the problem is not that it is blank, but that it has an unhandled COP.
A programmed device with an unhandled COP is just as troublesome.
A blank device when powered will reset itself every default COP period until you get it
into background mode.
This can be observed on a GB by scoping the reset pin.
 
This brings me to my first gripe.
The manual does not make it clear that even when enabled, the QG reset is input only!
Unlike most other devices, so you can't observe this on the QG.
 
Because of this resetting it is actually very easy to get a GB into BKGD mode.
Just hold reset low for at least the COP period and there you go!
 
Now it seems that as the QG has reset in only, this prevents the reset from getting
across to the BKGD module and so it doesn't work!
 
No problem you say! I will issue a "Background Debug Force Reset".
Well while this works normally, it DOES NOT work while the QG is in this mode.
 
It appears the only way to get a QG into active background mode while blank or COP
hiccuping is to hold BKGD low out of a POWER ON reset!
 
Now the P&E pod handles this by when it fails to connect it holds BKGD low and then
instructs you to cycle the power. The OSBDM has no such workaround and so you must hold
BKGD low yourself and cycle power then re-connect.
 
This brings me to my second gripe:
Why isn't an internal reset communicated to the BKGD module even if its not going out to the pin?
 
and my third one:
Why doesn't BKGD force reset work on a blank part?
 
Seems to me there is some issues in the silicon here
 
or in the manual?
 
or in my head?
 
or all three???
 
Regards
Peg

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