WM9715L
Production Data
CONTROLLING THE TOUCHPANEL DIGITISER
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
BIT
LABEL
DEFAULT
DESCRIPTION
78h
12
45W
0 (4-wire)
Touchpanel Type Selection
0: 4-wire
1: 5-wire
0:5
RPU
000001
Internal Pull-up resistor for Pen Detection
000000: RESERVED (do not use this setting)
000001: RPU/1 = TYP 68kΩ (most sensitive)
000010: RPU /2 = TYP 34kΩ
(68kΩ)
… (pull-up = RPU / binary value of RPU)
(Refer to page 9 for RPU specification)
8
PIL
0 (200µA)
Current used for pressure measurement
0: IP = 200µA
1: IP = 400µA
Table 23 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
BIT
LABEL
DEFAULT
DESCRIPTION
78h
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
13
RPR
0
0: Wake-up the AC-Link only (hold
SDATAIN high until controller sends warm
reset or cold reset)
1: Wake-up the WM9715L without waiting
for a reset signal from the controller
Table 24 Touchpanel Digitiser Control (Power Management)
PD Rev 4.0 December 2007
42
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
