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WAN0143 Schematic ( PDF Datasheet ) - Wolfson Microelectronics plc

Teilenummer WAN0143
Beschreibung ADA and MASK Timing on WM9712
Hersteller Wolfson Microelectronics plc
Logo Wolfson Microelectronics plc Logo 




Gesamt 6 Seiten
WAN0143 Datasheet, Funktion
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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






WAN0143 Datasheet, Funktion
WAN_0143
IMPORTANT NOTICE
Wolfson Microelectronics plc (WM) reserve the right to make changes to their products or to discontinue any product or service
without notice, and advise customers to obtain the latest version of relevant information to verify, before placing orders, that
information being relied on is current. All products are sold subject to the WM terms and conditions of sale supplied at the time of
order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability.
WM warrants performance of its products to the specifications applicable at the time of sale in accordance with WM’s standard
warranty. Testing and other quality control techniques are utilised to the extent WM deems necessary to support this warranty.
Specific testing of all parameters of each device is not necessarily performed, except those mandated by government
requirements.
In order to minimise risks associated with customer applications, adequate design and operating safeguards must be used by the
customer to minimise inherent or procedural hazards. Wolfson products are not authorised for use as critical components in life
support devices or systems without the express written approval of an officer of the company. Life support devices or systems are
devices or systems that are intended for surgical implant into the body, or support or sustain life, and whose failure to perform when
properly used in accordance with instructions for use provided, can be reasonably expected to result in a significant injury to the
user. A critical component is any component of a life support device or system whose failure to perform can be reasonably
expected to cause the failure of the life support device or system, or to affect its safety or effectiveness.
WM assumes no liability for applications assistance or customer product design. WM does not warrant or represent that any
license, either express or implied, is granted under any patent right, copyright, mask work right, or other intellectual property right of
WM covering or relating to any combination, machine, or process in which such products or services might be or are used. WM’s
publication of information regarding any third party’s products or services does not constitute WM’s approval, license, warranty or
endorsement thereof.
Reproduction of information from the WM web site or datasheets is permissible only if reproduction is without alteration and is
accompanied by all associated warranties, conditions, limitations and notices. Representation or reproduction of this information
with alteration voids all warranties provided for an associated WM product or service, is an unfair and deceptive business practice,
and WM is not responsible nor liable for any such use.
Resale of WM’s products or services with statements different from or beyond the parameters stated by WM for that product or
service voids all express and any implied warranties for the associated WM product or service, is an unfair and deceptive business
practice, and WM is not responsible nor liable for any such use.
ADDRESS:
Wolfson Microelectronics plc
Westfield House
26 Westfield Road
Edinburgh
EH11 2QW
Tel :: +44 (0)131 272 7000
Fax :: +44 (0)131 272 7001
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Rev 1.0 March 2004
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