Toshiba TLCS-900/H1 Series Manual page 428

3.19.3 Touch Detection Procedure
The Touch detection procedure shows procedure until a pen is touched by the screen and
it is detected.
By touching, TSI generates interrupt (INT4) and this procedure terminates. After an X/Y
position measuring procedure is terminated, return to this procedure and wait for the next
touch.
When the waiting state, make ON only the SPY switch ON and OFF the other 3 switches
(SMY, SPX and SMX).
The pull-down resistor that is connected to the P96/INT4/PX pin is ON when the SPX
switch is OFF.
During this waiting state, P96/INT4/PX pin's level is L because the internal Pull-down
resistors (PXD) between the X and Y directions in the touch screen are not connected and
INT4 is not generated.
When the pen touches the screen, P96/INT4/PX pin's level is H because the internal
resistors between the X and Y directions in the touch screen are connected and INT4 is
generated.
In order to avoid the generation of several interrupts from one touch, a debounce circuit
is used, as below.
This can ignore the pulse under the time which is set to TSICR1 register.
The circuit detects the rising of signal, counts-up the time of the counter which is set,
after count, receive the signal internal. During counting, when the signal is set to Low,
counter is cleared. And the state become to state of waiting a rising edge.
P96/INT4/PX pin
TSICR1
Debounce circuit
Figure 3.19.3 Block Diagram of Debounce Circuit
92CH21-426
TSICR0<TWIEN>, IIMC<I4EDGE>, P9FC<P96F>
Enables INT4 and
selects the Rising edge or
Falling edge of INT4
F/F
TMP92CH21
INT4
TSICR0
<PTST>
2009-06-19