WM8321 datasheet(128/253 Pages) WOLFSON

128 / 253 page

WM8321

Production Data

PD, February 2012, Rev 4.0

128

24 RESETS AND SUPPLY VOLTAGE MONITORING

24.1 RESETS

The WM8321 provides hardware and software monitoring functions as inputs to a Reset management

system. These functions enable the device to take appropriate action when power supplies are

critically low or if a hardware or software fault condition is detected.

There are different levels of Resets, providing different response mechanisms according to the

condition that caused the Reset event. Where applicable, the WM8321 will automatically return to the

ON state and resume normal operation as quickly as possible following a Reset.

A System Reset occurs in the event of a Power Sequence Failure, Device overtemperature, PVDD

undervoltage, Software ‘OFF’ request or VPMIC (LDO12) undervoltage condition. Under these

conditions, the WM8321 asserts the RESET

¯¯¯¯¯¯ pin and transitions to the OFF state. In the case of

VPMIC undervoltage, the WM8321 enters the BACKUP state. The contents of the Register map are

not reset under System Reset conditions.

A Device Reset occurs in the event of a Watchdog Timeout, Hardware Reset request or Converter

(LDO or DC-DC) Undervoltage condition. Under these conditions, the WM8321 asserts the RESET

¯¯¯¯¯¯

pin and transitions to the OFF state. The contents of the Register map are cleared to default values,

except for the RTC and software scratch registers, which are maintained. The WM8321 will

automatically return to the ON state after performing the Device Reset.

A Software Reset occurs when any value is written to Register 0000h, as described in Section 12.5.

In this event, the WM8321 asserts the RESET

¯¯¯¯¯¯ pin and transitions to the OFF state. The Register map

contents may or may not be affected, depending on the value of the SW_RESET_CFG field. See

Section 24.3 for further details of Software Reset configuration. The WM8321 will automatically return

to the ON state after performing the Software Reset.

A Power-On Reset occurs when the supply voltage is less than the Power-On Reset threshold, as

described in Section 24.4. In this event, the WM8321 is forced into the NO POWER state, as

described in Section 11.2. All the contents of the Register map are lost in the NO POWER state.

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