SLLSFE8B November 2024 – November 2025 TCAN2845-Q1 , TCAN2847-Q1
PRODUCTION DATA
Cyclic Wake can be used to self-wake the device using timer1 or timer2 period without a need for an external wake event. This feature behaves in a specific manner depending upon the SBC mode the device is in and if enabled. This function is available in normal, standby, fail-safe and sleep modes.
In normal and standby Cyclic Wake, at the start of the programmed on time, the device pulls nINT low for programmed-on time and release. The first on time pulse is ignored but each on-time afterward causes the interrupt to pulse low. Cyclic wake is enabled by using register 8'h25[3] for timer1 or 8'h26[3] for timer2. See Table 8-8 for registers used to program cyclic wake feature. Timers are configured using the respective registers. For cyclic wake to work in Normal and Standby modes, all existing interrupts need to be cleared. Interrupts take priority over cyclic wake function in the Normal and Standby modes. Set nINT_TOG=0b (default setting) for cyclic wake configuration. Setting nINT_TOG=1b causes the nINT pin to toggle during the on-time of the timer.
Cyclic wake can be enabled in fail-safe mode by using register 8'h0E[6]=1b. As VCC1 is off in fail-safe mode, nINT pin is not used. When enabled, the period selected for the timer needs to be 500ms, 1s or 2s (longer than tLDOOFF). When the on time takes place, the device determines if a fault is still present. If fault has not cleared, the device stays in fail-safe mode and repeats the process until the SWE timer times out at which time the device transitions to sleep mode. If fault has cleared, this is treated as a wake event and the device transitions to restart mode. Cyclic wake interrupt is reported at the CYC_WUP interrupt bit, INT_4[4].
Cyclic wake can be enabled in sleep mode by setting register 8'h4F[4]=1b and configuring the corresponding timer. After the configured timer period expires, the device wakes up and transition to restart mode where the LDOs are turned on. Cyclic wake interrupt is reported at the CYC_WUP interrupt bit, INT_4[4]. Once the device enters standby mode, the programmed long window starts and is expecting a WD trigger from the processor within this window. If this does not take place, the device considers this as a watchdog error and transition back to restart mode. Which then transition back to standby mode and expect a WD trigger within the long window. Even if VCC1 is on in sleep mode, this same procedure takes place.
| Address | Default | Field | Description |
|---|---|---|---|
| 8'h0E[6] | 0b | FSM_CYC_WK_EN | Setting to 1b enables the cyclic wake feature in fail-safe mode |
| 8'h25[3] | 0b | TIMER1_CYC_WK_EN | Setting to 1b associates the cyclic wake timer to timer1 |
| 8'h26[3] | 0b | TIMER2_CYC_WK_EN | Setting to 1b associates the cyclic wake timer to timer2 |
| 8'h4F[4] | 0b | SLP_CYC_WK_EN | Setting to 1b enables cyclic wake feature in sleep mode. |