Overview

Reset is used to restore the system to an initial state, which can be utilized for error recovery, system software reboot, and other functionalities.

Reset Types

The chip supports multiple reset types.

RTL8721DxRTL8720ERTL8726ERTL8713ERTL8730ERTL8721F

Reset Type	Description	Usage Method
Chipen	Reset generated by chip enable	Refer to Chip Enable
POR reset	Reset generated at power-on	Refer to BOD
BOR reset	Reset generated by undervoltage	Refer to BOD
DSLP	Reset generated when entering deep sleep mode	Refer to Power management
System reset	Software reset provided by the system	Refer to Software Reset
Warm reset	Software reset provided by the CPU	-
IWDG reset	Reset generated by independent watchdog timeout	Refer to WDG
WDG reset	Reset generated by system watchdog timeout	Refer to WDG

Reset Domains

RTL8721DxRTL8720ERTL8726ERTL8713ERTL8730ERTL8721F

Power Domain	Scope	Chipen	POR reset	BOR reset	DSLP	system reset	warm reset	IWDG reset	WDG reset
PD_AON	RTC	Y	Y	N	N	N*	N*	N	N*
PD_AON	Backup registers, Retention RAM, Wake pin, Trap pin	Y	Y	N	N	N	N	N	N
PD_AON PD_AON_OTP	IWDG OTPC	Y	Y	Y	Y	Y*	Y*	Y	Y*
PD_SYSON PD_SOC	All peripherals in SYSON power domain All peripherals in SOC power domain	Y	Y	Y	Y	N*	N*	Y	N*

• Y: Indicates that the corresponding module will be reset when the reset event occurs.

• N: Indicates that the corresponding module will not be reset when the reset event occurs.

• Y*: Indicates that the corresponding module will be reset by default when the reset event occurs, but can be configured not to reset.

• N*: Indicates that the corresponding module will not be reset by default when the reset event occurs, but can be configured to reset.

Note

• The register REG_AON_SYSRST_MSK can be used to control whether RTC, IWDG, and OTPC are reset under system reset and WDG reset. The register definition and default values are located in sysreg_aon.h.

• REG_LSYS_SYSRST_MSK0 and REG_LSYS_SYSRST_MSK1 can be used to control whether peripherals in PD_SYSON and PD_SOC power domains are reset under system reset and WDG reset. The register definitions and default values are located in sysreg_lsys.h.

• Warm reset can provide more flexibility regarding reset domains through REG_LSYS_SW_RST_CTRL. The register definition and default values are located in sysreg_lsys.h.

Obtaining Boot Reason

User can obtain the boot reason using the BOOT_Reason() function. Refer to Boot reason.

Preserving Pre-reset Information

User can store critical data in backup registers or Retention RAM located in the AON region to prevent data loss due to reset.

Note

The following reset types will still cause data loss in backup registers or Retention RAM:

• chipen

• POR reset

Backup Registers

RealTek provides 4 32-bit backup registers: BKUP_REG0(), BKUP_REG1(), BKUP_REG2(), and BKUP_REG3() for use. User can manipulate these registers using the provided APIs.

Note

The system may use certain bits in the backup registers. User should search the SDK to confirm if a specific bit is already in use before using it.

API

BKUP_Write

Item	Description
Function	Write a value to the corresponding backup register
Params	DwordIdx: The backup register to operate on (BKUP_REG0-3) WriteVal: The value to be written
Return	None

BKUP_Read

Item	Description
Function	Read the value from the corresponding backup register
Params	DwordIdx: The backup register to operate on (BKUP_REG0-3)
Return	The value of the corresponding backup register

BKUP_Set

Item	Description
Function	Set specific bits in the corresponding backup register
Params	DwordIdx: The backup register to operate on (BKUP_REG0-3) BitMask: The bits to be set
Return	None

BKUP_Clear

Item	Description
Function	Clear specific bits in the corresponding backup register
Params	DwordIdx: The backup register to operate on (BKUP_REG0-3) BitMask: The bits to be cleared
Return	None

Retention RAM

User can use the RRAM_DEV variable to store data in Retention RAM. The structure definition of this variable is RRAM_TypeDef, located in sysreg_lsys.h. Its structure member RRAM_USER_RSVD can be freely used by users.

Note

It is recommended that users prioritize using backup registers and only use Retention RAM when dealing with larger data volumes.

Software Reset Trigger Methods

User can execute a system reset by calling the System_Reset() function or by issuing a command. The definition of the System_Reset() function is as follows:

System_Reset

Item	Description
Function	Trigger a system software reset
Params	None
Return	None

Alternatively, the following command can be issued to any CPU to trigger a system software reset:

AT+RST