VR4102 datasheet(384/701 Pages) NEC

384 / 701 page

CHAPTER 19 PIU (TOUCH PANEL INTERFACE UNIT)

384

19.2 SCAN SEQUENCER STATE TRANSITION

Figure 19-4. Scan Sequencer State Transition Diagram

WaitPenTouch

DataScan

Interval

ADPortScan

CMDScan

Standby

Disable

PIUSeqEN=1

ADPSStart=1

PIUSeqEn=

TimeOut

Release &

AutoStop=1

Touch

auto

ADPSStart=

PIUSeqEN=1

& PIUmode=01

PIUSeqEn=0

Release

PIUSeqEn=0

PIUPWR=0

PIUPWR=1

Reset=1

PIUSeqEn=1

& ScanStart=1

ScanStart=1

PIUSeqEn=0 or ScanStop=1

• Disable state

In this state, the A/D converter is in standby mode, the output pins are in touch detection mode (no PIU

interrupt), and the input pins are in mask mode (to prevent misoperation when an undefined input is applied).

• 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.

• ADPortScan state

This is the state in which voltage is measured at the three A/D converter’s 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 (PIUABxREG). After the four ports are scanned, a PadCMDIntr interrupt occurs.

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.

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