
WM9712L
CONTROLLING THE TOUCHPANEL DIGITISER
Production Data
w
PD Rev 4.0 December 2003
42
All touchpanel functions are accessed and controlled through the AC-Link interface.
PHYSICAL CHARACTERISTICS
The physical characteristics of the touchpanel interface are controlled through register 78, as shown
below.
REGISTER
ADDRESS
78h
BIT
LABEL
DEFAULT
DESCRIPTION
12
45W
0 (4-wire)
Touchpanel Type Selection
0: 4-wire
1: 5-wire
Internal Pull-up resistor for Pen Detection
000000: RESERVED (do not use this setting)
000001: R
PU
/1 = TYP 64k
(most sensitive)
000010: R
PU
/2 = TYP 32k
… (pull-up = R
PU
/ binary value of RPU)
(Refer to page 9 for R
PU
specification)
Current used for pressure measurement
0: I
P
= 200
μ
A
1: I
P
= 400
μ
A
0:5
RPU
000001
(64k
)
8
PIL
0 (200
μ
A)
Table 25 Touchpanel Digitiser Control (Physical Characteristics)
POWER MANAGEMENT
To save power, the touchpanel digitiser and the pen-down detector can be independently disabled
when they are not used. The power consumption of the pen-down detector is normally negligible,
except when the pen is down.
The state of the digitiser and pen down detector is controlled by the following bits.
REGISTER
ADDRESS
78h
BIT
LABEL
DEFAULT
DESCRIPTION
15:14
PRP
00
Pen ADC/AUX ADC enable
00 – Pen digitiser off, pen detect off, no
wake-up on pen down (default)
01 – Pen digitiser powered off, pen detect
enabled, touchpanel digitiser wakes up
(changes to state 11) on pen-down
10 – Pen digitiser off, pen detect enabled,
no wake-up on pen down
11 – Pen digitiser and pen detect enabled
Wake-up on pen-down mode
0: Wake-up the AC-Link only (hold
SDATAIN high until controller sends warm
reset or cold reset)
1: Wake-up the WM9712L without waiting
for a reset signal from the controller
13
RPR
0
Table 26 Touchpanel Digitiser Control (Power Management)