WM9713L_06 Datasheet, PDF (70/108 Pages) Wolfson Microelectronics plc – AC 97 Audio + Touchpanel CODEC

WM9713L
Pre-Production
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.
REGISTER BIT LABEL
ADDRESS
78h
7:6 MSK
Table 55 MASK Input Control
DEFAULT
DESCRIPTION
00
MASK input control (see Table 56)
MSK[1-0]
EFFECT OF SIGNAL ON MASK PIN
00
Mask has no effect on conversions GPIO input disabled (default)
01
Static; ‘hi’ on MASK pin stops conversions, ‘lo’ has no effect.
10
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.
11
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.
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-
• After every touchpannel ADC conversion (in normal mode, COO=0)
• After every set of 3 conversions (co-ordinate mode, COO=1)
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.
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PP Rev 3.0 June 2006
70