WM8351 datasheet(113/330 Pages) WOLFSON

113 / 330 page

Production Data

WM8351

PD, April 2012, Rev 4.5

113

By default, the DO_CONF output will be set low when the WM8351 enters the OFF state and set high

on every transition from OFF to ACTIVE, re-triggering the external ‘genie’. Also, by default, the

internal control registers will be reset when the WM8351 enters the OFF state. This behaviour can be

changed using the RECONFIG_AT_ON register bit. If RECONFIG_AT_ON is set to 0, then the

control registers will not be reset when going into the OFF state, and the DO_CONF output will

remain set high after the first powering up of the chip, regardless of subsequent state transitions.

De-selection of RECONFIG_AT_ON should be used with caution, as this can potentially lead to

system failures in some applications. If RECONFIG_AT_ON is set to 0, and an OFF event occurs,

then it is possible that control registers will not be set to the intended start-up values when the

WM8351 subsequently returns to the ON state. The impact of this will depend upon the hardware and

software of the particular target application, and is not necessarily a risk in every instance. Please

contact Wolfson Applications support if further guidance is required on this topic.

Note that RECONFIG_AT_ON should never be set to 0 in Custom Modes 01, 10 or 11. Setting this bit

to 0 may result in erroneous behaviour and deviation from the custom configuration settings. Under

default settings, the control registers are always reset in the OFF state.

The register fields DO_CONF and RECONFIG_AT_ON are defined in Table 63.

ADDRESS

BIT

LABEL

DEFAULT

DESCRIPTION

R6 (06h)

Interface

Control

CONFIG_D

ONE

Tells the system that the PIC micro has

completed its programming.

0 = Programming still to be done

1 = Programming complete

Only applies when CONFIG pins[1:0] = 00.

RECONFIG

_AT_ON

Selects whether to reset the registers in the

OFF state and whether to reload the device

configuration from the PIC when an ON

event occurs.

0 = Do not reset registers in the OFF state.

Do not load configuration data when an ON

event occurs.

1 = Reset registers in the OFF state. Load

configuration from the PIC when an ON

event occurs.

Note that, in development mode, the device

configuration from the PIC is always loaded

when first powering up the chip.

This bit must always be set to default (1) in

Custom Modes 01, 10 and 11.

Table 63 Start-Up Control in Development Mode

Note:

if the WM8351 enters the BACKUP state as a result of an undervoltage condition (see

Section 18), then the control registers will be reset, but DO_CONF will remain high. When the supply

voltage rises and device comes out of BACKUP, the DO_CONF output will still be high. If the

DO_CONF signal is used to trigger an external ‘genie’ device, then this may not work, as the

DO_CONF has remained high through the BACKUP state transition, and the WM8351 device will

become locked in the PRE-ACTIVE state when an ON event occurs.

This problem may be avoided by ensuring that the ‘genie’ monitors the LINE voltage in order to

recognise the undervoltage condition, and that it verifies the I2C Acknowledge signal on the

secondary interface (GPIO10 and GPIO11) to determine whether it can execute its programming

function.

14.4.3

CONFIGURING THE WM8351 IN DEVELOPMENT MODE

The WM8351 can be configured in Development mode by writing to control bits that determine its

startup behaviour. The locations of these register bits are shown in Table 64 below. A typical

configuration sequence would include writes to some or all of the registers listed. If none of the

highlighted bits in any given register needs to be changed from its default, then no write to that

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