WM9705 datasheet(43/55 Pages) WOLFSON

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WM9705

Production Data

PD Rev 4.4 August 2006

ADR[2-0]

CHANNEL

000

none

001

X- plate

010

Y-plate

011

Pressure Conversion

100

BMON

101

AUXADC

110

PHONE

111

PCBEEP

Table 24 Conversion Address to Channel Map

If BUSY flag is enabled (BSEN bit in reg 78h set ‘1’) then the BUSY pin will remain high until the

conversion in complete, whereby it will transition low.

This signal is output onto pin 47, EAPD/BUSY where it may be observed by the controller if

required as an interrupt. (Note that use of this BUSY flag clearly precludes use of the EAPD

external amplifier power down bit, but as the WM9705 has integrated headphone amplifier with it’s

own power down bit PR6 in register 26h, this should not be a problem. If BSEN is not set, then

EAPD operates as normal)

If SLOT method is enabled (SLEN bit in register 76h is set ‘1’) then the data is output into the

chosen slot and the appropriate slot tag bit set. Choice of which slot the data is written into is

made by setting bits SLT[2-0] in register 76h. The following table shows which slot versus [2-0]

value.

SLT[2-0]

OUTPUT SLOT FOR

DIGITISER DATA

000

001

010

011

100

101

110

Table 25 Pen ADC Slot Select

When the conversion result has been read, then another conversion may be commenced as

required. In the event of another conversion being requested, then the stored result from the last

conversion will be overwritten when the new conversion has been completed.

However, if the WAIT bit is set in register 78h, then once a conversion is complete, the current

conversion result may not be written into the results register, until the previous conversion result

has been read. The sequence will halt at the finish of this current conversion, waiting for the

results register to be cleared. Note that this does allow the controller to slow down the rate of

conversions, so effectively determining the overall rate of conversion.

CONVERSION CONTROL

Control of ADC conversions, and screen driving functions, is by one of three methods:

•

Polling method

•

Polled Co-ordinate method

•

Continuous method

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