Production Data
WM9715L
If the SLEN bit is set to ‘1’, then the touchpanel data appears on the AC-Link slot selected by the
SLT control bits, as shown below. The Slot 0 ‘tag’ bit corresponding to the selected time slot is
asserted whenever there is new data on that slot.
REGISTER
ADDRESS
BIT
LABEL
SLEN
DEFAULT
DESCRIPTION
76h
3
0
Slot Readback Enable
0: Disabled (readback through register only)
1: Enable (readback slot selected by SLT)
2:0
SLT
110
AC’97 Slot Selection for Touchpanel Data
000: Slot 5
001: Slot 6
…
101: Slot 10
110: Slot 11
111: RESERVED
Table 28 Returning Touchpanel Data Through an AC-Link Time Slot
TOUCHPANEL SETTLING TIME
For accurate touchpanel measurements, some settling time may be required between the switch
matrix applying a voltage across the touchpanel plate and the ADC sampling the signal. This time
delay function is built into the WM9715L and can be programmed as shown below.
REGISTER
ADDRESS
BIT
7:4
LABEL
DEL
DEFAULT
DESCRIPTION
76h
0000
Touchpanel ADC Settling Time
(1 frame)
Table 29 Touchpanel Settling Time Control (1)
DEL
DELAY
DELAY
(TIME)
20.8µs
41.7µs
83.3µs
167µs
333µs
667µs
1ms
(AC-LINK FRAMES)
0000
0001
0010
0011
0100
0101
0110
0111
1000
1001
1010
1011
1100
1101
1110
1111
1
2
4
8
16
32
48
64
96
128
160
192
224
256
288
1.33ms
2ms
2.67ms
3.33ms
4ms
4.67ms
5.33ms
6ms
No delay, switch matrix always on
Table 30 Touchpanel Settling Time Control (2)
The total time for co-ordinate or auxiliary measurements to complete is the delay time DEL, plus one
AC-Link frame (20.8µs). For a pressure measurement, the time taken is DEL plus two AC-Link
frames (41.6µs).
PD Rev 4.0 December 2007
45
w
WOLFSON [ WOLFSON MICROELECTRONICS PLC ]
