EP4CE40 datasheet(243/488 Pages) ALTERA

243 / 488 page

Chapter 8: Configuration and Remote System Upgrades in Cyclone IV Devices

8–79

Remote System Upgrade

May 2013

Altera Corporation

Cyclone IV Device Handbook,

Volume 1

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.

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.

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.

Table 8–26. Control Register Contents After an Error or Reconfiguration Trigger Condition

Reconfiguration Error/Trigger

Control Register Setting In Remote Update

nCONFIG

reset

All bits are 0

nSTATUS

error

All bits are 0

CORE triggered reconfiguration

Update register

CRC error

All bits are 0

Wd time out

All bits are 0

Table 8–27. 10-MHz Internal Oscillator Specifications

Minimum

Typical

Maximum

Unit

6.5

MHz

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