EP4CE30F29C7N Datasheet, PDF (243/488 Pages) Altera Corporation – Cyclone IV Device Handbook, Volume 1

Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices
Remote System Upgrade
8–79
The remote system upgrade status register is updated by the dedicated error
monitoring circuitry after an error condition, but before the factory configuration is
loaded.
Table 8–26. Control Register Contents After an Error or Reconfiguration Trigger Condition
Reconfiguration Error/Trigger
nCONFIG reset
nSTATUS error
CORE triggered reconfiguration
CRC error
Wd time out
Control Register Setting In Remote Update
All bits are 0
All bits are 0
Update register
All bits are 0
All bits are 0
User Watchdog Timer
The user watchdog timer prevents a faulty application configuration from indefinitely
stalling the device. The system uses the timer to detect functional errors after an
application configuration is successfully loaded into the Cyclone 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 remote
system upgrade circuitry appends 17'b1000 to form the 29-bits value for the watchdog
timer. The granularity of the timer setting is 2¹⁷ cycles. The cycle time is based on the
frequency of the 10-MHz internal oscillator or CLKUSR (maximum frequency of
40 MHz).
Table 8–27 lists the operating range of the 10-MHz internal oscillator.
Table 8–27. 10-MHz Internal Oscillator Specifications
Minimum
5
Typical
6.5
Maximum
Unit
10
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 the 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.
Errors during configuration are detected by the CRC engine. Functional errors must
not exist in the factory configuration because it is stored and validated during
production and is never updated remotely.
May 2013 Altera Corporation
Cyclone IV Device Handbook,
Volume 1