wm9713 Wolfson Microelectronics plc, wm9713 Datasheet - Page 78

• Manufacturer Part Number: wm9713
• Description: Ac?97 Audio + Touchpanel Codec
• Manufacturer: Wolfson Microelectronics plc

WM9713L
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MASK INPUT CONTROL
Sources of glitch noise, such as the signals driving an LCD display, may feed through to the
touchscreen plates and affect measurement accuracy. In order to minimise this effect, a signal may
be applied to MASK (pin 47 / pin 3) to delay or synchronise the sampling of any input to the ADC.
The effect of the MASK signal depends on the the MSK bits of register 78h (bits [7:6]), as described
below.
Table 55 MASK Input Control
Table 56 Controlling the MASK Feature
Note that pin 47 / pin 3 can also be used as a GPIO (see “GPIO and Interrupt Control” section), or to
output the ADA signal (see below).
THE ADA SIGNAL
Whenever data becomes available from the touchpanel ADC, the internal ADA (ADC Data Available)
signal goes high and remains high until the data has been read from register 7Ah (if SLEN = 0) or
until it has been sent out on an AC-Link slot (if SLEN = 1).
ADA goes high either-
ADA can be used to generate an interrupt, if the AW bit (register 52h, bit 12) is set (see “GPIO and
interrupt control” section)
It is also possible to output the ADA signal on pin 47 / pin 3, if this pin is not used as a GPIO. The
GE4/6 bit must be set to ‘0’ to achieve this (see “GPIO and interrupt control” section).
Alternatively, ADA can be read from bit 12 in register 54h.
78h
REGISTER
MSK[1-0]
ADDRESS
•
•
00
01
10
11
After every touchpannel ADC conversion (in normal mode, COO=0)
After every set of 3 conversions (co-ordinate mode, COO=1)
Mask has no effect on conversions GPIO input disabled (default)
Static; ‘hi’ on MASK pin stops conversions, ‘lo’ has no effect.
Edge triggered; rising or falling edge on MASK pin delays conversions
by an amount set in the DEL[3-0] register. Conversions are asynchronous to the
MASK signal.
Synchronous mode; conversions wait until rising or falling edge on MASK initiates
cycle; screen starts to be driven when the edge arrives, the conversion sample
being taken a period set by DEL[3-0] after the edge.
7:6
BIT
MSK
LABEL
EFFECT OF SIGNAL ON MASK PIN
00
DEFAULT
Mask Input Control
see Table 56 for details
DESCRIPTION
PP Rev 3.2 September 2008
Pre-Production
78