Answers Database

FPGA CONFIGURATION: Effect of power-glitch invoked reset on XC2000/3000 devices


Record #134

Problem Title:
FPGA CONFIGURATION: Effect of power-glitch invoked reset on XC2000/3000
devices



Problem Description:



Solution 1:




Effects of power-glitch invoked reset on XC2000 and XC3000 devices

XC2000:

if power dips to the 5v - 3v range;
   the device will still be operational, but a global reset
   should be initiated and held there until device has 4.7 to 5v again

if power dips to the 3v - 1v range;
   depending on how long this state is invoked the device will either
   reprogram (if it was at low-power long enough) -OR-
   the device will experience brown out (if it was NOT at low-power
   long enough) in which it is in an unknown state.

  NOTE: the lower the voltage drops, the less time is required
	for a reprogram

   The workaround for this is to bring reset high for 6 microsec
   and then bring BOTH reset and D/P pins low for 6 microsec.  This will
   bring the device back to the Clear Configuration Memory state of
   configuration.

if power dips to around 0v;
   the device will reprogram.  If reset was activated when the glitch
   occured then the device will clear congfiguration memory, but will
   not proceed with configuration until reset is released.


XC3000:
POWERDOWN pin should be tied to VCC

if power drops to the 3v-2v range;
   the device will reprogram if power is low long enough  -OR-
   nothing will happen if power is NOT low long enough and the
   internal latches will retain the configuration memory.


 NOTE: the lower the voltage drop the less time is required
       to initiate a reprogram

   Here's the data for a glitch occuring at 2-3 volts:

   2.9 volts - pulse width >= 13us
   2.8 volts - pulse width >= 9 us
   2.7 volts - pulse width >= 4 us
   2.6 volts - pulse width >= 1 us
   2.3 volts - pulse width >= .5 us

   In general if the power glitch is > 13us then the device
   should reconfigure automatically.

if power drops below 2v;
   the device will almost certainly reprogram as long as this
   glitch is longer than 2 microsec.




End of Record #134