User Documentation

The Watchdog class provides the S32K1xx Watchdog API.

Public API

The public API of Watchdog class consists of following constructors and methods:

/**
 * Default constructor (disables the watchdog)
 */
Watchdog() { disableWatchdog(); }

/**
 * Constructor (starts the watchdog)
 * \param[in] timeout Watchdog timeout in milliseconds
 * \param[in] clockSpeed Speed of WDOG input clock in hertz
 */
explicit Watchdog(uint32_t const timeout, uint32_t const clockSpeed = DEFAULT_CLOCK_SPEED)
{
    enableWatchdog(timeout, false, clockSpeed);
}

/**
 * Enables the watchdog
 * \param[in] timeout Watchdog timeout in milliseconds
 * \param[in] interruptActive Activates the Watchdog interrupt WDOG_EWM_IRQn
 * \param[in] clockSpeed Speed of WDOG input clock in hertz
 */
static void enableWatchdog(
    uint32_t const timeout,
    bool const interruptActive = false,
    uint32_t const clockSpeed  = DEFAULT_CLOCK_SPEED);
/**
 * Disables the watchdog
 */
static void disableWatchdog();
/**
 * Services the watchdog
 */
static void serviceWatchdog();
/**
 * Check that the configuration of the watchdog as set when enables has not been changed
 * \param[in] timeout Watchdog timeout in milliseconds
 * \param[in] clockSpeed Speed of WDOG input clock in hertz
 */
static bool checkWatchdogConfiguration(
    uint32_t const timeout, uint32_t const clockSpeed = DEFAULT_CLOCK_SPEED);
/**
 * Start testing the low byte of the counter. If the test is successful the WD will trigger an
 * Ecu Reset
 */
static void startFastTestLow();
/**
 * Start testing the high byte of the counter. If the test is successful the WD will trigger an
 * Ecu Reset
 */
static void startFastTestHigh();
/**
 * Execute the WD fast test. On first call this will trigger the test for the low byte, then on
 * second call it will trigger the test for the high byte of the counter.
 * Afterwards it should always return true, indicating that the WD test was successful.
 *
 * \param timeout delay for the watchdog to timeout
 *
 * \return
 * - false = the check was started, but it was unsuccessful
 * - true = the check executed successfully since the last power-on reset, no further check is
 *          needed for this cycle
 * - does not return = the check was started and watchdog has reset the ECU as expected
 */
static bool executeFastTest(uint32_t timeout);
/**
 * After a successful fast test the WD can be set in user mode where CS[TST]==01
 */
static void setUserMode();
/**
 * Returns the number of times the watchdog has been serviced
 */
static uint32_t getWatchdogServiceCounter();

The startFastTestLow method starts the fast testing of low byte of the watchdog counter, The watchdog timeout value is set in the TOVAL register. The low byte of the counter is selected for testing, by assigning 10b to the control and status register test bits i.e CS[TST] = 10b.

The startFastTestHigh method starts the fast testing of high byte of the watchdog counter, The watchdog timeout value is set in the TOVAL register. The high byte of the counter is selected for testing, by assigning 11b to the control and status register test bits i.e CS[TST] = 11b.

Fast Testing of Watchdog

The fast test is implemented according to the safety reference manual (Chapter 5.6.9.2: Fast testing of the watchdog, S32K1xx Series Safety Manual, Rev. 7.1, 12/2021). This means the high and low byte are tested separately, one after the other.