WM9705 datasheet(41/55 Pages) WOLFSON

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WM9705

Production Data

PD Rev 4.4 August 2006

TIMING OF PEN DIGITISER OPERATIONS

Timing of pen digitiser operations is linked to the AC link frame timing. A single ADC conversion

takes one frame to complete, including taking a sample, converting it, and passing it into the

practise to allow time for screen plates to settle etc, much lower rates of conversion are

anticipated.

The ADC is powered up only for the duration of each conversion, therefore power consumption is

a linear function of the conversion rate chosen.

CONTROL OF PEN DIGITISER FUNCTIONS

Control of the digitiser functions is via control bits written into control registers via the AC link. The

following table shows the name, function and location of the control bits for the pen digitser

section of the WM9705. Address locations are chosen to avoid unexpected corruption of normal

AC’97 audio codec operation, using mostly vendor specific addresses from the AC’97 adddress

map.

Reg Name

D15

D14

D13

D12

D11

D10

Default

76h

Digitizer control

POLL ADR2 ADR1 ADR0 COO

CTC

CR1

CR0

DEL3 DEL2 DEL1 DEL0 SLEN SLT2 SLT1

SLT0

0006h

78h

Digitizer control

PRP1 PRP0

RPR PDEN PINV BSEN BINV WAIT

PIL

PHIZ MSK1 MSK0 PDD3 PDD2 PDD1 PDD0

0000h

7Ah

Pen Digitizer data

PNDN ADR2 ADR1 ADR0

D11

D10

0000h

INDEX 76H – DIGITISER CONTROL WORD 1 – READ/WRITE REGISTER

BIT

LOCATION

FUNCTION

POLL

Starts a single polled conversion (resets itself at completion)

ADR[2-0]

14-12

Sets the address of the single conversion in polled mode, or extra conversions in Co-

ordinate or Continuous mode. See Table 24.

COO

Selects a co-ordinate set of conversions

CTC

Starts continuous conversion operation

CR[1-0]

9,8

Sets continuous conversion rate

DEL[3-0]

7-4

Sets the delay between screen being driven and X or Y sample being taken

SLEN

Slot enable bit; allows conversion results to be output onto chosen slot

SLT[2-0]

2-0

Slot select bits; choose which slot to output data results in

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