| Kinetis SDK Demo Applications User Guide 1.0.0-beta Freescale Semiconductor, Inc.

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Watchdog Timer Demo User Guide
Watchdog Timer Demo

User guide on how to use this application. More...

### Watchdog Timer Demo User Guide

# Getting started

1. Power on.
   - Open terminal tools, such as Putty.
   - Download the code to the board.
2. When the code is running, the watchdog is enabled. The code continuously refreshes the watchdog to prevent the CPU reset.
3. When the LED starts blinking, the "Watchdog example running, Loop #: xx, press <SW> to start watchdog timeout..." message displays on the terminal. on the TWR-K64F120M board, the blink led is yellow LED, and on the FRDM-K64F120M board, the blink led is green LED.
4. When the SW key is pressed, on the TWR-K64F120M board, the yellow LED blinks rapidly signifying that the watchdog is about to expire, on the FRDM-K64F120M board, the red LED blinks rapidly signifying that the watchdog is about to expire(Because the FRDM-K64F120M board has a tri-color LED and at the very beginning the program light the green led. When the red one start to blink, red and green mix togther, the led color that you can see is yellow.).
5. When the watchdog signals a reset, the "Watchdog(COP) Reset" message and "Watchdog(cop) reset count: xx" message output to the terminal.

# Note

1) On the TWR-K64F120M board, the pull-up resistor R49 is labeled with "DNP", so this register should be installed first. The SW key is SW1. 2) On the TWR-K64F120M board, the information which is output to the terminal may be incorrect and sometimes display "External Pin Reset" message. This occurs when the watchdog signals a reset to the system and the K20 also sends a pin reset to the K64 MCU through TXS0101. Sometimes, the TXS0101 can't pull up the pin in time and the duration of the low level of this pin is long. When this occurs, the watchdog reset status is changed by the external pin reset and the message "External Pin Reset" is output to the terminal. 3) On the FRDM-K64F120M board, the pull-up resistor R1 is labeled with "DNP", so this register should be installed first. The SW key is SW2.