Difference between revisions of "AURA SOM/AURA Hardware/Power and Reset/Reset scheme and control signals"
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* '''WDOG_B''', pulled-up with 100 kohm | * '''WDOG_B''', pulled-up with 100 kohm | ||
* '''PMIC_INTn''', pulled-up with 10 kohm | * '''PMIC_INTn''', pulled-up with 10 kohm | ||
| − | Furthermore, the following control signals are | + | Furthermore, the following control signals are avaible: |
* '''SOM_PGOOD''', | * '''SOM_PGOOD''', | ||
Revision as of 07:40, 13 February 2024
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Reset scheme and control signals[edit | edit source]
The following picture shows the simplified block diagram of the reset scheme and voltage monitoring.
AURA SOM provides the following reset signals:
- SYS_nRST
- CPU_PORn, pulled-up with 100 kohm. This signal, pilot by the PMIC, reset SoC's CPU and onboard eMMC and ethernet PHY.
- WDOG_B, pulled-up with 100 kohm
- PMIC_INTn, pulled-up with 10 kohm
Furthermore, the following control signals are avaible:
- SOM_PGOOD,
- PMIC_ON_REQ, pulled-down with 100 kohm
- PMIC_STBY_REQ, pulled-down with 100 kohm
- ONOFF, pulled-up with 100 kohm
TBD: indicare le connessioni del segnale di reset verso altri device interni (come per esempio la NOR SPI
CPU_PORn[edit | edit source]
The following devices can assert this active-low signal:
- PMIC
- multiple-voltage monitor: this device monitors critical power voltages and triggers a reset pulse in case any of these exhibits a brownout condition
Since SPI NOR flash can be used as a boot device, CPU_PORn is connected to this device too. This guarantees it is in a known state when reset signal is released.
Handling CPU-initiated software reset[edit | edit source]
By default, i.MX93 processor does not assert any external signal when it initiates a software reset sequence. Also, default software reset implementation does not guarantee that all processor registers are reset properly.
For these reasons, it is strongly recommended to use a different approach that, in combination with the use of a processor's watchdog timer (WDT), provides a full hardware reset in case a software reset is issued.
This technique is implemented in DESK-MX9-L. At the software level, U-Boot and Linux kernel software reset routines make use of the processor's WDT #1 to assert the WDOG1_WDOG reset signal. This signal in turn is routed to WDOG_ANY pad (MUX mode ALT_0). At the hardware level, this signal is connected to the WDOG_B PMIC pin driving a PMIC reset.
