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PDF WAN0143 Data sheet ( Hoja de datos )
| Número de pieza | WAN0143 | |
| Descripción | ADA and MASK Timing on WM9712 | |
| Fabricantes | Wolfson Microelectronics plc | |
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WAN-0143
ADA and MASK Timing on WM9712
INTRODUCTION
WM9712 SETUP
This applications note has been created to detail the timing of the MASK and ADA (ADC Data
Available) signals on the WM9712 device. This applications note should be used in conjunction with
the latest WM9712 datasheet.
The WM9712 has many additional functions to aid the design of portable applications. Pin 47 of the
device can be configured for either MASK input, ADA output or standard GPIO functionality. The
MASK function can be used to pause and control auxiliary ADC conversions. The ADA function can
be used to indicate when data becomes available from the auxiliary ADC. The timing associated
with both signals is detailed in the following sections of this document.
The WM9712 device must be configured to setup the function of pin 47. The three possible setups
are:
• MASK Input Function
• ADA Function
• General GPIO
To set the device into one of the three above modes the following configurations should be used.
PIN 47 MODE
MASK
ADA
GPIO
REGISTER 56H BIT 4 SETTING
(GPIO FUNCTION SELECT)
1
1
0
Table 1 WM9712 Pin 47 Configuration
REGISTER 4CH BIT 4 SETTING
(PIN DEFINED AS INPUT OR OUTPUT)
1 (Input)
0 (Output)
1 or 0 (GPIO can be Input or Output)
MASK FUNCTION
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) to delay or synchronise the sampling of any input to the ADC. The effect
of the MASK signal depends on the MSK[1-0] bits of register 78h, as described below.
MSK[1-0]
00
01
10
11
EFFECT OF SIGNAL ON MASK PIN
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.
Table 2 Controlling the MASK Feature
WOLFSON MICROELECTRONICS plc
www.wolfsonmicro.com
March 2004, Rev 1.0.
Copyright 2004 Wolfson Microelectronics plc
1 page  
WAN_0143
SUMMARY
Pin 47 of the WM9712 has three possible functions which are:
• MASK input,
• ADA output or
• General GPIO.
The modes and timings associated with MASK and ADA are detailed in this document. Further
information on these functions and the GPIO operation is detailed in the WM9712 datasheet.
APPLICATION SUPPORT
If you require more information or require technical support please contact Wolfson Microelectronics
Applications group through the following channels:
Email:
Telephone:
Fax:
Mail:
+44 (0)131 272 7070
+44 (0)131 272 7001
Applications at the address on last page.
or contact your local Wolfson representative.
Additional information may be made available from time to time on our web site at
http://www.wolfsonmicro.com
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Rev 1.0 March 2004
5
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