[ASAHI KASEI]
Power Down of Touch Screen
When the TSPD bit in Touch Screen Control register (07h) is set to "1", touch screen driver and A/D converter goes to
power-down mode. As the register value is still preserved in power-down mode, the register can be accessed under
power-down mode.
Waiting State for Pen Interrupt and INT Signal
When the PW bit in Touch Screen Control register (07h) is set to "1", the AK4533 goes to the state which waits for the
interrupt caused by touching the screen. INT pin outputs "H" through internal schmitt trigger buffer while the
screen is being touched. INT signal can notify to the external circuit that the screen is touched.
The AK4533 supplies VA to TSY_BTM with keeping TSY_TOP and TSX_TOP open state under Waiting State for
Pen Interrupt. And TSX_BTM is connected to AGND through the internal resistor, Ro.
If the screen is not touched, the current doesn't flow from Y-Plate to X-Plate because two plates are not connected, and TSX_BTM is
"L" because this terminal is connected to AGND through Ro.
When the screen is touched, the current flows from Y-Plate to X-Plate. As the resistor value of touch screen is much smaller than that
of Ro, the level of TSX_BTM is "H". This INT signal can be used as the interrupt signal to the micro controller. When the screen is
touched, INT goes "H", and returned "L" when the pen is released.
TSX_BTM
TSX_TOP
TPY_TOP
Ro
PW
touched
released
VA
TPY_BTM
INT
INT
Processor
Figure 20. Waiting for Pen Interrupt
<Revision 0.9a>
33
July 00
AKM [ ASAHI KASEI MICROSYSTEMS ]
