5.2 MCU RESET MODE
(Submit Feedback)The MCU Reset mode is the default mode of the ATA6847 after a Power-On Reset. It is the Reset execution state of the device. This mode ensures that the NRES pin is pulled down for a defined time to allow the microcontroller to be reset in a controlled manner.
The INH pin, if available, is driven high.
In the MCU Reset mode, the LIN transceiver is unable to transmit or receive data (LIN Standby mode, see Section LIN Transceiver). The gate drive unit is in GDU OFF mode. The SPI is disabled. All registers will be reset to initial value. If the mode transition was triggered by the NRES pin being driven externally, the SPI communication is disabled only until tReset expires. The LDO voltage regulators (VDDx) and the overtemperature detection are active. The watchdog is disabled.
In the MCU Reset mode, the DOPMCR Register cannot be programmed and is set to Standby.
The following events will cause the ATA6847 to transition to MCU Reset mode:
- Transitioning from Sleep mode or Deep Sleep mode after detecting a wake-up event or interrupt event.
- After a watchdog time-out or when the watchdog in Window mode is triggered too early.
- An attempt is made to reconfigure the watchdog control register while the ATA6847 is in Normal mode.
- For the ATA6847-5050: If the RSTLVL bit in the DOPMCR
register has been set to ‘
1’ and VVDD1 < VVDD1_UV_Set - For the ATA6847/ATA6847L: VVDD1 < VVDD1_UV_IO_Set
- For the ATA6847-5050, ATA6847-5033: VVDD2 < VVDD2_UV_IO_Set
MCU Reset Mode and VDD Undervoltage Events
(Submit Feedback)For ATA6847-5050, if the RSTLVL bit is set to
‘1’ (default), the device will enter MCU Reset mode after
detecting a VDD1 undervoltage (VVDD1 < VVDD1_UV_Set).
The device will stay in the MCU Reset mode until VDD1 recovers (VVDD1 > VVDD1_UV_Clear) and then resets, restarting the Reset pulse length timer.
If VDD1 undervoltage is detected when the device is in MCU Reset mode, the Reset pulse length timer will remain on hold until VDD1 recovers and will then be reset and restarted.
The ATA6847 device will leave the MCU Reset mode and enter Standby mode after the tReset time expires (see Device Operating Modes).
For ATA6847-3333 or ATA6847-5033, the device will enter MCU Reset mode only after Power-on start-up, after detecting a Watchdog Reset event, or after detecting VVDD1 < VVDD1_UV_IO_Set, independent of the value of RSTLVL bit from the DOPMCR register. In this case, the device will start the Reset pulse length timer after the device enters the MCU Reset mode and VVDD1 > VVDD1_UV_IO_Clear has been detected. As soon as the timer has expired, the device will transition to Standby mode.
Reset Input and Output (NRES)
(Submit Feedback)The NRES pin is asserted when the ATA6847 enters MCU Reset mode. The ATA6847 also enters MCU Reset mode when the NRES pin is pulled low externally. The ATA6847 can only exit MCU Reset mode when the NRES pin is not driven “low” externally.