Difference between revisions of "AURA SOM/AURA Hardware/Power and Reset/Reset scheme and control signals"
m (→Reset scheme and control signals) (Tag: Visual edit) |
m (→Reset scheme and control signals) (Tag: Visual edit) |
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| Line 60: | Line 60: | ||
|PMIC | |PMIC | ||
|SoC, onboard eMMC and PHY ETH, External | |SoC, onboard eMMC and PHY ETH, External | ||
| − | | | + | |Reset peripherals internal and external to the SOM after a power-on sequence |
|- | |- | ||
|'''SOM_PGOOD''' | |'''SOM_PGOOD''' | ||
| Line 66: | Line 66: | ||
|SOM | |SOM | ||
|External | |External | ||
| − | | | + | |Turn on the external circuitry of the SOM |
|- | |- | ||
|'''PMIC_INTn''' | |'''PMIC_INTn''' | ||
| − | |PMIC Output, pulled-up with 10 kohm inside the SOM | + | |PMIC Output, open drain, pulled-up with 10 kohm inside the SOM |
|PMIC | |PMIC | ||
|SoC and External | |SoC and External | ||
Revision as of 11:03, 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
- WDOG_B, pulled-up with 100 kohm
- CPU_PORn, pulled-up with 100 kohm. This signal, pilot by the PMIC, reset SoC's CPU and onboard eMMC and ethernet PHY.
- PMIC_INTn, pulled-up with 10 kohm
Furthermore, some 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
The electrical and functional characteristics of these signals are listed in the following table:
| Signal | Type | Driven | Affect | Purpose |
|---|---|---|---|---|
| SYS_nRST | PMIC Input, pulled-up inside the PMIC | Externally | PMIC | |
| WDOG_B | PMIC Input, pulled-up with 100 kohm inside the SOM | Externally or SoC | PMIC | |
| CPU_PORn | PMIC Output, open drain, pulled-up with 100 kohm inside the SOM | PMIC | SoC, onboard eMMC and PHY ETH, External | Reset peripherals internal and external to the SOM after a power-on sequence |
| SOM_PGOOD | Monitor Output, 3V3 LVTTL | SOM | External | Turn on the external circuitry of the SOM |
| PMIC_INTn | PMIC Output, open drain, pulled-up with 10 kohm inside the SOM | PMIC | SoC and External | |
| PMIC_ON_REQ | PMIC Input, pulled-down with 100 kohm inside the SOM | Externally or SoC | PMIC | |
| PMIC_STBY_REQ | PMIC Input, pulled-down with 100 kohm inside the SOM | Externally or SoC | PMIC | |
| ONOFF | SoC Input, pulled-up with 100 kohm inside the SOM | Externally | SoC |
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.
Ciclo di reset completo utilizzare
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.
