WM9715L Datasheet, PDF (51/77 Pages) Wolfson Microelectronics plc – AC’97 Audio and Touchpanel CODEC

Production Data
INTERRUPT CONTROL
WM9715L
THE ADCIRQ PIN
The WM9715L has three interrupt pins:
• ADCIRQ is a dedicated interrupt pin to indicate that AUXADC data is available for reading
(see “Touchpanel interface”)
• PENDOWN is a dedicated interrupt pin to indicate that the resistive touchpanel
connected to the WM9715L is being touched (see “Touchpanel interface”)
• GENIRQ is a general-purpose interrupt pin, which can indicate a number of different
events.
In a typical use case with touchscreen measurements running continuously, “AUXADC data
available” is the most frequent type of interrupt event from the WM9715L. In the interest of
minimizing software overheads, it is recommended to use the dedicated ADCIRQ pin to transmit this
type of interrupt.
The ADCIRQ output is enabled using registers 56h and 4Ch.
REGISTER BIT LABEL DEFAULT
ADDRESS
4Ch
4
GC4 1
56h
4
GE4 1
Table 34 Enabling the ADCIRQ pin
DESCRIPTION
ADCIRQ output enable
ADCIRQ is enabled when both GC4 and GE4 are
set to ‘0’.
To disable ADCIRQ, set both bits to ‘1’.
Other combinations (0/1, 1/0) are reserved.
THE PENDOWN PIN
In a typical use case, PENDOWN is the second most frequent type of interrupt after ADCIRQ. In the
interest of minimizing software overheads, it is recommended to use the dedicated PENDOWN pin to
transmit this type of interrupt.
The PENDOWN output is enabled using registers 56h and 4Ch.
REGISTER BIT LABEL DEFAULT
ADDRESS
4Ch
3
GC3 1
56h
3
GE3 1
Table 35 Enabling the PENDOWN pin
DESCRIPTION
PENDOWN output enable
PENDOWN is enabled when both GC4 and GE4 are
set to ‘0’.
To disable PENDOWN, set both bits to ‘1’.
Other combinations (0/1, 1/0) are reserved.
THE GENIRQ PIN
The GENIRQ pin transmits a logical OR of up to five individual interrupt events:
• Over-temperature (see “Thermal Sensor”)
• COMP1 events, e.g. dead battery alarm (see “Battery Alarm and Analogue Comparators”)
• COMP2 events, e.g. low battery alarm (see “Battery Alarm and Analogue Comparators”)
• ADCIRQ
• PENDOWN
When the host processor receives an interrupt, it needs to read register 54h in order to determine
which event triggered the interrupt. As a result, GENIRQ is best suited for interrupts that occur rarely,
and where longer response times can be tolerated. ADCIRQ or PENDOWN interrupts should only be
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PD Rev 4.0 December 2007
51