Toshiba TLCS-900/H1 Series Manual page 491

3.19.3 Touch detection procedure
The touch detection procedure includes the procedure starting from when the pen is
touched onto the touch screen and until the pen-touch is detected.
Touching the screen generates the interrupt (INT4) and terminates this procedure. After
an X/Y position measuring procedure is terminated, return to this procedure to wait for the
next touch.
When waiting for a touch with no contact, set only the SPY switch to ON and set all other
three switches (SMY, SPX, SMX) to OFF. At this time, the pull-down resistor built in the
P96/INT4/PX pin is set ON.
In this state, because the internal X- and Y-direction resistors in the touch screen are not
connected, the P96/INT4/PX pin is set to Low by the internal pull-down resistor (PXD),
generating no INT4 interrupt.
When a next pen-touch is given, the X- and Y-direction internal resistors in the touch
screen are connected, which sets the P96/INT4/PX pin to High and generates an INT4
interrupt.
To avoid generating more than one INT4 interrupt by one pen-touch, the debounce circuit
as shown below is provided. Setting debounce time in the TSICR1 register ignores pulses
whose time equals to or is below the set time.
The debounce circuit detects a rising of signal to count up a set debounce counter time
and then captures the signal into the inside after counting. When the signal turns to "L"
during counting, the counter is cleared, starting to wait for a rising edge again.
P96/INT4 pin
TSICR1
Debounce circuit
Figure 3.19.3 Block diagram of debounce circuit
92CF30-489
TSICR0<TWIEN>, IIMC<I4EDGE>,
Enables INT4,
And select the Rising
or Falling of INT4
F/F
TMP92CF30
INT4
TSICR0
<PTST>
2009-06-12