
CHAPTER 9
PIU (TOUCH PANEL INTERFACE UNIT)
User’s Manual U14579EJ2V0UM
129
9.2
Scan Sequencer State Transition
Figure 9-4. Scan Sequencer State Transition Diagram
Disable
Reset = 1
PIUPWR = 1
PIUSEQEN = 1 &
ADPSSTART = 1 &
PIUMODE = 00
PIUSEQEN = 1 &
PADATSTART = 1 &
PIUMODE = 00
Release &
PADATSTOP = 1
PIUPWR = 0
ADPSSTART = 1
Timeout
PIUSEQEN = 1 &
PADSCANSTART = 1 &
PIUMODE = 00
PIUSEQEN = 0 or
PADSCANSTOP = 1
auto
Standby
PIUSEQEN = 1 &
PIUMODE = 01
PIUSEQEN = 0
WaitPenTouch
ADPortScan
ADPSSTART = 1
Touch
PIUSEQEN = 0
PenDataScan
Interval
NextScan
CmdScan
Release
PIUSEQEN = 0
(1) Disable state
In this state, the A/D converter is in standby mode, the output pins are in touch detection mode and the input
pins are in mask mode (to prevent misoperation when an undefined input is applied).
State transition to Suspend mode is possible, however, it is necessary to wait for the time set by STABLE(5:0)
area in the PIUSTBLREG register to ensure stabilization.
(2) Standby state
In this state, the unit is in scan idle mode. The touch panel is in low-power mode (0 V voltage is applied to the
touch panel and the A/D converter is in disable mode). Normally, this is the state from which various mode
settings are made.
Caution
State transitions occur when the PIUSEQEN bit is active, so the PIUSEQEN bit must be set
as active after each mode setting has been completed.
(3) ADPortScan state
This is the state in which voltage is measured at the A/D converter’s general-purpose port and audio input
port. After the A/D converter is activated and voltage data is obtained, the data is stored in the PIU’s internal
data buffer (PIUABnREG register). After the two ports are scanned, an A/D port scan interrupt occurs inside
the PIU. After this interrupt occurs, the ADPSSTART bit is automatically set as inactive and the state changes
to the state in which the ADPSSTART bit was active.