ad7879-1acbz-rl Analog Devices, Inc., ad7879-1acbz-rl Datasheet - Page 25

• Manufacturer Part Number: ad7879-1acbz-rl
• Description: Low Voltage Controller For Touch Screens
• Manufacturer: Analog Devices, Inc.

ADC Channel (Control Register 1 Bits[14:12])
The ADC channel is selected by Bits[14:12] of Control Register 1
(CHNL ADD2 to CHNL ADD0). A complete list of channel
addresses is given in Table 19.
For Mode 0 (single-channel) conversion, the channel is selected
by writing the appropriate CHNL ADD2 to CHNL ADD0 code
to Control Register 1.
For sequential channel conversion, channels to be converted are
selected by setting bits corresponding to the channel number in
the Control Register 3 for slave and master mode sequencing.
Table 19. Codes for Selecting Input Channel and Normal or Ratiometric Conversion
Channel
0
1
2
3
4
5
6
7
8
9
12
13
14
15
SER/DFR
0
0
0
0
0
0
0
0
1
1
1
1
1
1
1
1
CHNL ADD[2:0]
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
1 1 1
1 1 0
1 0 1
1 0 0
0 1 1
0 1 0
0 0 1
0 0 0
Analog Input
X+ (Y position)
Y+ (X position)
X+ (Z1 touch pressure)
Y− (Z2 touch pressure)
AUX
VBAT
TEMP
X+ (Y position)
Y+ (X position)
X+ (Z1 touch pressure)
Y− (Z2 touch pressure)
AUX
VBAT
TEMP
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For both single-channel and sequential conversion, a normal
conversion (single-ended) is selected by clearing the SER/ DFR
bit in Control Register 2 (Bit 9). Ratiometric (differential)
conversion is selected by setting the SER/ DFR bit.
PENIRQ Enable (Control Register 1, Bit 15)
The AD7879 has a dual function output that performs as
PENIRQ or INT depending on the pen interrupt enable bit
(Bit 15 of Control Register 1). When this bit is set to 0, the
pin is working as a pen interrupt and it goes low whenever the
screen is touched. When the pen interrupt enable bit is set to 1,
the pin interrupt request is disabled and the pin functions as INT .
X Switches
Off
On
X+ off, X− on
X+ off, X− on
Off
Off
Off
Off
On
Off
Off
Off
Off
Off
Invalid address
Invalid address
Y Switches
On
Off
Y+ on, Y− off
Y+ on, Y− off
Off
Off
Off
On
Off
Off
Off
Off
Off
Off
+REF
Y+
X+
Y+
Y+
V
V
V
V
V
V
V
V
V
V
CC
CC
CC
CC
CC
CC
CC
CC
CC
CC
AD7879
−REF
Y−
X−
X−
X−
GND
GND
GND
GND
GND
GND
GND
GND
GND
GND