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• Disable state
In this state, the A/D converter is in standby status, the output pins are in touch detection status (no PIU
interrupt), and the input pins are in mask status (to prevent misoperation when an undefined input is applied).
• Standby state
In this state, the PIU is in scan idle status. The touch panel is in low-power status (0 V voltage is applied to the
touch panel and the A/D converter is in disable status). Normally, this is the state in which various mode
settings are made.
Caution Since a state transition occurs when the PIUSEQEN bit is active, the PIUSEQEN bit must be
set as active after various mode settings have been completed.
• ADPScan state
This is the state in which voltage is measured at the A/D converter's three general-purpose ports and one 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, n = 0 to 3). After the four ports are scanned, an A/D port scan interrupt
request occurs. After this interrupt occurs, the ADPSSTART bit is automatically set as inactive and the PIU
enters the state in which the ADPSSTART bit has been set as active.
• CMDScan state
In this state, the A/D converter operates according to various settings. Voltage data from one port only is
fetched based on a combination of the touch panel pin setting (TPX(1:0), TPY(1:0)) and the selection of an
input port (TPX(1:0), TPY(1:0), AUDIOIN, ADIN(2:0)) to the A/D converter. Use PIUCMDREG register to make
the touch panel pin setting and to select the input port.
• WaitPenTouch state
This is a standby state in which the PIU waits for a touch panel's "touch" status. When the PIU detects a touch
panel's "touch" status, a touch panel contact status change interrupt request occurs inside the PIU. At this
point, if the PADATSTART bit is active, the PIU enters the DataScan state. During the WaitPenTouch state, it
is possible to enter Suspend mode because the panel state can be detected even while the TClock is stopped.
• DataScan state
This is the state in which touch panel coordinates are detected. The A/D converter is activated and four data
for each coordinate are sampled.
Caution If one complete set of coordinate data is not obtained during the interval between one set
of coordinate data and the next coordinate data, a data lost interrupt request occurs.
• Interval state
This is the standby state in which the PIU waits for the next coordinate sampling period or the touch panel's
"release" status. After the touch panel status is detected, the time period specified via PIUSIVLREG register
elapses before the transition to the DataScan state. If the PIU detects the "release" status within the specified
time period, a touch panel contact status change interrupt request occurs inside the PIU. At this point, the PIU
enters the WaitPenTouch state if the PADATSTOP bit is active. If the PADATSTOP bit is inactive, it enters to
the DataScan state after the specified time period has elapsed.
CHAPTER 14 TOUCH PANEL INTERFACE UNIT (PIU)
User's Manual U14272EJ3V0UM
279
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