Altera Corporation
12–7
September 2004
Stratix Device Handbook, Volume 2
Remote System Configuration with Stratix & Stratix GX Devices
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Determines the user watchdog timer’s settings if the timer is enabled
(remote configuration mode)
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If the user watchdog timer is not reset after a predetermined amount
of time, it times-out and the system loads the factory configuration
data back to the Stratix or Stratix GX device
If a system encounters an error while loading application configuration
data, or if the device re-configures due to nCONFIG assertion, the Stratix
or Stratix GX device loads the factory configuration. The remote system
configuration register determines the reason for factory re-configuration.
Based on this information, the factory configuration determines which
application configuration needs to be loaded.
Application Configuration
The application configuration is the configuration data received from the
remote source and updated into different locations or pages of the
memory storage device (excluding the factory default page).
Watchdog Timer
A watchdog timer is a circuit that determines whether another
mechanism functions properly. The watchdog timer functions like a time-
delay relay that remains in the reset state while an application runs
properly. This action periodically sends a reset command from the
working application to the watchdog timer. Stratix and Stratix GX
devices are equipped with a built-in watchdog timer for remote system
configuration.
A user watchdog timer prevents a faulty application configuration from
indefinitely stalling the Stratix or Stratix GX device. The timer functions
as a counter that counts down from an initial value, which is loaded into
the device from the factory configuration. This is a 29-bit counter, but you
use only the upper 12 bits to set the value for the watchdog timer. You
specify the counter value according to your design needs.
The timer begins counting once the Stratix or Stratix GX device goes into
user mode. If the application configuration does not reset the user
watchdog timer after the specified time, the timer times-out. At this point,
the Stratix or Stratix GX device is re-configured by loading the factory
configuration and resetting the user watchdog timer.
1
The watchdog timer is disabled in local configuration mode.