WM9705SEFTSLASHV datasheet(47/55 Pages) WOLFSON

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WM9705

Production Data

PD Rev 4.4 August 2006

Figure 23 Control of ADC Conversions : Continuous Method

DELAY FUNCTION

In order to allow time for the plates to charge to a steady voltage when the screen drive switches

are closed, a programmable delay may be applied which delays the sampling of the appropriate

plate voltage by the ADC. This delay is at least one frame (1/48kHz) in duration, but may be

increased by writing a value to the DEL[3-0] bits in register 76h. These set delays as follows:

DEL[3-0]

DELAY

(FRAMES)

DELAY

(uS)

DEL[3-0]

DELAY

(FRAMES)

DELAY

(uS)

20.8

1666

41.7

128

2000

83.3

160

2333

166.7

192

2666

333.3

224

3000

666.7

256

3333

1000

288

3666

1333

infinite

Table 27 Programmable Screen Drive Delay

Note that code 15 is used as a special mode, where the plates are driven permanently on, the

switch matrix setting controlled by the value selected by ADR[2-0]. Thus the plates may be

permanently set to drive X screen, Y screen, pressure configuration, or the auxiliary input channel

permanently connected to the ADC input. For further information please see the section on

Auxiliary Conversions.

Different types of continuous conversion with delay set to 0 (1 frames)

CTC = 1, CC=11, Coord = 0, ADR = 001 ( 0x76 = 0x1700 ) = X Measurement every 64 AC Link Frames

DELAY

CONVERT

Conversion 1 result available

DELAY

CONVERT

Conversion 2 result available

Conversion 1

Conversion 2

64 Frames

CTC = 1, CC=00, Coord = 1, ADR = 000 ( 0x76 = 0x0C00 ) = X and Y Measurement every 512 AC Link Frames

DELAY

CONVERT

Conversion 1 - X

result available

DELAY

CONVERT

Conversion 1

Conversion 2

512 Frames

CONVERT

DELAY

CONVERT

DELAY

Conversion 2 - X

result available

Conversion 2 - Y

result available

CTC = 1, CC=01, Coord = 1, ADR = 100 ( 0x76 = 0x4C01 ) = X, Y and BMON Measurement every 256 AC Link Frames

DELAY

CONVERT

Conversion 1

256 Frames

CONVERT

DELAY

CONVERT

DELAY

Conversion 1 - Y

result available

Conversion 2 - X

result available

DELAY

CONVERT

Conversion 1

256 Frames

CONVERT

DELAY

CONVERT

DELAY

Conversion 2 - Y

result available

Conversion 2 - BMON

result available

Conversion 1 - BMON

result available

SYNC

ADC Mode

Pen Data

ADC Mode

SYNC

Pen Data

ADC Mode

Pen Data

SYNC

Conversion 1 - Y

result available

Conversion 1 - X

result available

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