EP4CE40 datasheet(236/488 Pages) ALTERA

236 / 488 page

8–72

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

Remote System Upgrade

Cyclone IV Device Handbook,

May 2013

Altera Corporation

Volume 1

Figure 8–32 shows the transitions between the factory configuration and application

configuration in remote update mode.

After power up or a configuration error, the factory configuration logic writes the

remote system upgrade control register to specify the address of the application

configuration to be loaded. The factory configuration also specifies whether or not to

enable the user watchdog timer for the application configuration and, if enabled,

specifies the timer setting.

1 Only valid application configurations designed for remote update mode include the

logic to reset the timer in user mode. For more information about the user watchdog

timer, refer to the “User Watchdog Timer” on page 8–79.

If there is an error while loading the application configuration, the remote system

upgrade status register is written by the dedicated remote system upgrade circuitry of

the Cyclone IV device to specify the cause of the reconfiguration.

The following actions cause the remote system upgrade status register to be written:

■ nSTATUS

driven low externally

■

Internal cyclical redundancy check (CRC) error

■

User watchdog timer time-out

■

A configuration reset (logic array nCONFIG signal or external nCONFIG pin assertion)

The Cyclone IV device automatically loads the factory configuration when an error

occurs. This user-designed factory configuration reads the remote system upgrade

status register to determine the reason for reconfiguration. Then the factory

configuration takes the appropriate error recovery steps and writes to the remote

system upgrade control register to determine the next application configuration to be

loaded.

Figure 8–32. Transitions Between Configurations in Remote Update Mode

Set Control Register

and Reconfigure

Set Control Register

and Reconfigure

Reload a Different Application

Application n

Configuration

Application 1

Configuration

Factory

Configuration

Configuration Error

Power Up

Configuration

Error

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