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:
General Description:
Effects of power-glitch invoked reset on XC2000 and XC3000
devices.
Solution 1:
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 - Last Modified: 11/23/98 08:18 |
