Parallel Flash Loader Intel® FPGA IP User Guide

ID 683698
Date 7/23/2021

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Document Table of Contents User Watchdog Timer

The user watchdog timer prevents faulty configuration from stalling the device indefinitely. The system uses the timer to detect functional errors after a configuration image is successfully loaded into the FPGA.

The user watchdog timer is a time counter that runs at the pfl_clk frequency. The timer begins counting after the FPGA enters user mode and continues until the timer reaches the watchdog time out period. You must periodically reset this timer by asserting the pfl_reset_watchdog pin before the watchdog time-out period. If the timer does not reset before the watchdog time-out period, the PFL IP core detects watchdog time-out error and initiates a reconfiguration to load the factory image.

Instantiate the watchdog timer reset circuitry in the configuration image loaded into the FPGA. Connect one output signal from the reset circuitry to the pfl_reset_watchdog pin of the PFL in the CPLD to periodically send a reset signal to the user watchdog timer. To reset the watchdog timer correctly, hold the pfl_reset_watchdog pin high or low for at least two pfl_clk cycles.

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