EP4SE360F35I4 Datasheet, PDF (398/432 Pages) Altera Corporation – This section provides a complete overview of all features relating to the Stratix IV device family, which is the most architecturlly advanced

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Chapter 10: Configuration, Design Security, and Remote System Upgrades in Stratix IV Devices
Dedicated Remote System Upgrade Circuitry
User Watchdog Timer
The user watchdog timer prevents a faulty application configuration from stalling the
device indefinitely. The system uses the timer to detect functional errors after an
application configuration is successfully loaded into the Stratix IV device.
The user watchdog timer is a counter that counts down from the initial value loaded
into the remote system upgrade control register by the factory configuration. The
counter is 29 bits wide and has a maximum count value of 2²⁹. When specifying the
user watchdog timer value, specify only the most significant 12 bits. The granularity
of the timer setting is 2¹⁷ cycles. The cycle time is based on the frequency of the
10-MHz internal oscillator. Table 10–18 lists the operating range of the 10-MHz
internal oscillator.
Table 10–18. 10-MHz Internal Oscillator Specifications (Note 1)
Minimum
Typical
Maximum
4.3
5.3
10
Note to Table 10–18:
(1) These values are preliminary.
Units
MHz
The user watchdog timer begins counting after the application configuration enters
device user mode. This timer must be periodically reloaded or reset by the application
configuration before the timer expires by asserting RU_nRSTIMER. If the application
configuration does not reload the user watchdog timer before the count expires, a
time-out signal is generated by the remote system upgrade dedicated circuitry. The
time-out signal tells the remote system upgrade circuitry to set the user watchdog
timer status bit (Wd) in the remote system upgrade status register and reconfigures the
device by loading the factory configuration.
1 To allow remote system upgrade dedicated circuitry to reset the watchdog timer, you
must assert the RU_nRSTIMER signal active for a minimum of 250 ns. This is equivalent
to strobing the reset_timer input of the ALTREMOTE_UPDATE megafunction high
for a minimum of 250 ns.
The user watchdog timer is not enabled during the configuration cycle of the device.
Errors during configuration are detected by the CRC engine. Also, the timer is
disabled for factory configurations. Functional errors should not exist in the factory
configuration because it is stored and validated during production and is never
updated remotely.
1 The user watchdog timer is disabled in factory configurations and during the
configuration cycle of the application configuration. It is enabled after the application
configuration enters user mode.
Stratix IV Device Handbook
Volume 1
September 2012 Altera Corporation