AD7879 datasheet(20/36 Pages) AD

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AD7879

Rev. 0 | Page 20 of 36

DETAILED REGISTER DESCRIPTIONS

All addresses and default values are expressed in hexadecimal.

Table 10. Control Register 1

Address

Name

Data

Bit

Description

Default

Value

0x01

Disable PENIRQ

Pen interrupt enable.

0x0000

0 = PENIRQ pin is enabled.

1 = PENIRQ is disabled and INT enabled.

CHNL ADD[2:0]

14:12

ADC Channel address for manual conversion (mode 01).

111 = X+ input (Y position).

110 = Y+ input (X position).

101 = X+ (Z1) input for touch-pressure calculation.

100 = Y− (Z2) input (used for touch-pressure measurement).

011 = AUX input1.

010 = VBAT input1.

001 = temperature measurement.

000 = not applicable.

ADC MODE[1:0]

11:10

ADC mode.

00 = no conversion.

01 = single conversion2.

10 = conversion sequence (slave mode)2.

11 = conversion sequence (master mode).

ACQ[1:0]

9:8

ADC acquisition time.

00 = 4 clock periods (2 μs).

01 = 8 clock periods (4 μs).

10 = 16 clock periods (8 μs).

11 = 32 clock periods (16 μs).

Note that the acquisition time does not apply to the temperature sensor channels; the

temperature channel has a constant settling time of 16 μs.

TMR[7:0]

7:0

Conversion interval timer.

Starts at 550 μs and continues to 9.440 ms in steps of 35 μs.

Note that in slave mode, the conversion interval timer starts to count as soon as the

conversion sequence is finished; in master mode, it starts to count again only if the screen

remains touched. If the screen is released, the timer stops counting and, on the next screen

touch, a conversion starts immediately.

1 If GPIO is enabled, AUX and VBAT are both ignored. If AUX and VBAT are both selected, and GPIO is disabled, AUX is ignored, and VBAT is measured.

2 Note that these settings clear to 00 at the end of the conversion sequence if the conversion interval timer bits in Control Register 1 (0x01) Bits 7:0 = 0x00h at the end of

the conversion sequence.

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