EP2S90F1020C5 Datasheet, PDF (671/768 Pages) Altera Corporation – Stratix II Device Handbook, Volume 1

Remote System Upgrades with Stratix II and Stratix II GX Devices
After power up or a configuration error, the factory configuration logic
should write the remote system upgrade control register to specify the
page address of the application configuration to be loaded. The factory
configuration should also specify whether or not to enable the user
watchdog timer for the application configuration and, if enabled, specify
the timer setting.
The user watchdog timer ensures that the application configuration is
valid and functional. After confirming the system is healthy, the
user-designed application configuration should reset the timer
periodically during user-mode operation of an application configuration.
This timer reset logic should be a user-designed hardware and/or
software health monitoring signal that indicates error-free system
operation. If the user application configuration detects a functional
problem or if the system hangs, the timer is not reset in time and the
dedicated circuitry updates the remote system upgrade status register,
triggering the device to load the factory configuration. The user
watchdog timer is automatically disabled for factory configurations.
1 Only valid application configurations designed for remote
update mode include the logic to reset the timer in user mode.
1 For more information about the user watchdog timer, see “User
Watchdog Timer” on page 8–20.
If there is an error while loading the application configuration, the remote
system upgrade status register is written by the Stratix II or Stratix II GX
FPGA’s dedicated remote system upgrade circuitry, specifying the cause
of the reconfiguration. Actions that cause the remote system upgrade
status register to be written are:
■ nSTATUS driven low externally
■ Internal CRC error
■ User watchdog timer time out
■ A configuration reset (logic array nCONFIG signal or external
nCONFIG pin assertion)
Stratix II and Stratix II GX FPGAs automatically load the factory
configuration located at page address zero. This user-designed factory
configuration should read the remote system upgrade status register to
determine the reason for reconfiguration. The factory configuration
should then take appropriate error recovery steps and write to the remote
system upgrade control register to determine the next application
configuration to be loaded.
Altera Corporation
January 2008
8–11
Stratix II Device Handbook, Volume 2