Watchdog timer operation in Embedded C - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start the watchdog timer.

Embedded C

WDTCTL = [1];  // Start watchdog timer with password and interval

Drag options to blanks, or click blank then click option'

AWDTPW | WDTCNTCL | WDT_MRST_32

BWDTPW | WDTHOLD | WDT_MRST_32

CWDTPW | WDTCNTCL | WDT_MRST_64

DWDTPW | WDTHOLD

Attempts:

3 left

💡 Hint

Common Mistakes

Using WDTHOLD stops the watchdog timer instead of starting it.

Forgetting to include the password WDTPW causes the write to fail.

The watchdog timer control register must be set with the password (WDTPW), clear counter (WDTCNTCL), and the interval select bits (WDT_MRST_32) to start the timer.

2fill in blank

medium

Complete the code to reset (kick) the watchdog timer inside the main loop.

Embedded C

while(1) {
    // Your code here
    [1];  // Reset watchdog timer
}

Drag options to blanks, or click blank then click option'

AWDTCTL = WDTPW | WDTHOLD | WDT_MRST_32

BWDTCTL = WDTPW | WDTHOLD

CWDTCTL = WDTPW | WDTCNTCL | WDT_MRST_64

DWDTCTL = WDTPW | WDTCNTCL | WDT_MRST_32

Attempts:

3 left

💡 Hint

Common Mistakes

Using WDTHOLD stops the watchdog timer instead of resetting it.

Not including the password WDTPW causes the reset to fail.

Resetting the watchdog timer requires writing to WDTCTL with the password, clear counter bit, and interval bits to prevent a reset.

3fill in blank

hard

Fix the error in the watchdog timer stop code.

Embedded C

void stop_watchdog() {
    WDTCTL = [1];  // Stop watchdog timer
}

Drag options to blanks, or click blank then click option'

AWDTPW | WDTCNTCL

BWDTPW | WDTHOLD

CWDTPW | WDT_MRST_32

DWDTHOLD | WDTCNTCL

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting the password WDTPW causes the stop command to be ignored.

Using WDTCNTCL clears the counter but does not stop the timer.

To stop the watchdog timer, write WDTPW (password) combined with WDTHOLD to WDTCTL.

4fill in blank

hard

Fill both blanks to configure the watchdog timer interval and mode.

Embedded C

WDTCTL = WDTPW | [1] | [2];  // Configure watchdog timer

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AWDTCNTCL

BWDTHOLD

CWDT_MRST_64

DWDT_MRST_128

Attempts:

3 left

💡 Hint

Common Mistakes

Using WDTHOLD stops the timer instead of configuring it.

Choosing the wrong interval bits causes unexpected timer behavior.

WDTCNTCL clears the timer counter, and WDT_MRST_64 sets the interval mode to 64 cycles.

5fill in blank

hard

Fill all three blanks to create a safe watchdog reset function with stop and start.

Embedded C

void reset_watchdog() {
    WDTCTL = WDTPW | [1];  // Stop watchdog
    // Some critical code here
    WDTCTL = WDTPW | [2] | [3];  // Restart watchdog
}

Drag options to blanks, or click blank then click option'

AWDTHOLD

BWDTCNTCL

CWDT_MRST_32

DWDT_MRST_128

Attempts:

3 left

💡 Hint

Common Mistakes

Not stopping the watchdog before critical code can cause unwanted resets.

Forgetting to clear the counter when restarting causes immediate reset.

First, stop the watchdog with WDTHOLD. Then restart it by clearing the counter (WDTCNTCL) and setting the interval (WDT_MRST_32).