WM9705 datasheet(42/55 Pages) WOLFSON

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WM9705

Production Data

PD Rev 4.4 August 2006

INDEX 78H – DIGITISER CONTROL WORD 2 – READ/WRITE REGISTER

BIT

LOCATION

FUNCTION

PRP[1:0]

15:14

Pen digitiser power down bit control bits:

00 – Pen digitiser powered down, pen detect disabled, no wakeup on pen down (default)

01 – Pen digitiser powered off, pen detect enabled, wakeup on pen down enabled

10 – Pen digitiser powered off, pen detect enabled, no wakeup on pen down

11 – Pen digitiser powered up

RPR

Enables PR4 reset on pen down wake up

PDEN

causes conversions and screen drives to stop when pen is not down

PINV

Inverts sense of PENDET output: Default ‘0’ causes PEN = ‘down’ to give a ‘1’ output

BSEN

BUSY flag enable. Outputs converter BUSY signal on pin 47. ‘1’ = converter busy, goes

low at end of conversion to indicate result available

BINV

Invert sense of BUSY flag output

WAIT

WAIT bit; setting this bit causes conversion operations to halt when a result is about to

be written to the data register 7Ah, if the last stored result has not yet been read.

Conversions commence again once the result has been read

PIL

Pressure current select (‘0’=200uA, ‘1’=400uA)

PHIZ

Sets PHONE and PCBEEP inputs to be High impedance by disconnecting them from

mixer via an internal switch. Setting bit low opens the switch. Setting bit high closes

the switch. Default setting is low.

MSK[1:0]

5:4

Selects what effect MASK input has:

00 = MASK pin ignored

01 = Mask pin is static; ‘hi’ halts conversions

10 = Mask pin is edge sensitive; rising or falling edge delays conversions by DEL [3-0]

11 = Mask pin becomes a synchronise input; conversions happen after edge

PDD[3:0]

3:0

Pen detect comparator threshold

0 to Vmid in 15 steps; 0h = use zero power comparator with Vmid threshold

1 = Vmid/15 threshold

15 = Vmid threshold

INDEX 7AH – DIGITISER DATA WORD OUTPUT – READ REGISTER ONLY

BIT

LOCATION

FUNCTION

PNDN

Indicates whether Pen is Down; ‘1’ = ‘Down’

ADR[2:0]

14:12

Conversion Address; Indicates which channel the following result is for

D[11:0]

11:0

ADC output result

READBACK OF PEN DIGITISER RESULTS

Readback

conversion

results

from

either

pen

co-ordinate

conversions,

pressure

measurements, or auxiliary conversion, is via the AC link interface.

Readback may be performed either by reading from the read only register 7Ah via the AC link, or

by enabling SLOT mode (by writing SLEN = 1 in register 76h) where results are placed into the

AC link data slots by WM9705, and sent back to the controller.

The readback word contains the 12 bit data in the lsb locations, plus a 3 bit header in the next 3

bit locations, whose value corresponds to the channel that the data was converted from. Other

bits are padded with zero values. Channel addressing is the same as the address requested for

the conversion, as follows:

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