
CHAPTER 9
PIU (TOUCH PANEL INTERFACE UNIT)
User’s Manual U14579EJ2V0UM
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9.7
Data Lost Generation Conditions
The PIU issues a data lost interrupt when any of the following four conditions exist.
1.
Data for one coordinate has not been obtained within the interval period
2.
The A/D port scan has not been completed within the time set via PIUSTBLREG register
3.
Transfer of the next coordinate data has begun while valid data for both pages remains in the buffer
4.
The next data transfer starts while there is valid data in the ADPortScan buffer
Once a data lost interrupt occurs, the sequencer is forcibly changed to the Standby state.
The causes and responses are shown below for the four conditions.
(1) When data for one coordinate has not been obtained within the interval period
(a) Cause
This condition occurs when the AIU has exclusive use of the A/D converter and the PIU is therefore unable
to use the A/D converter.
If a data lost interrupt occurs frequently, implement a countermeasure that temporarily prohibits the AIU’s
use of the A/D converter.
(b) Response
After clearing the data lost interrupt by writing 1 to the PADDLOSTINTR bit of the PIUINTREG register, set
the PIUCNTREG register’s PADATSTART bit or PADSCANSTART bit to restart the coordinate detection
operation. Once the data lost interrupt is cleared, the page in which the loss occurred becomes invalid. If the
valid data prior to the data loss is needed, be sure to save the data that is being stored in the page buffer
before clearing the data lost interrupt.
(2) When the A/D port scan has not been completed within the time set via PIUSTBLREG register
(a) Cause
Same as cause of condition (1)
(b) Response
After clearing the data lost interrupt by writing 1 to the PADDLOSTINTR bit of the PIUINTREG register, set
the PIUASCNREG register’s ADPSSTART bit to restart the A/D port scan operation. Once the data lost
interrupt is cleared, the page in which the loss occurred becomes invalid. If the valid data prior to the data
loss is needed, be sure to save the data that is being stored in the page buffer before clearing the data lost
interrupt.