
User’s Manual U14272EJ3V0UM
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CHAPTER 14 TOUCH PANEL INTERFACE UNIT (PIU)
14.1 General
The PIU uses the on-chip A/D converter to detect the X and Y coordinates of pen contact locations on a touch
panel and to scan the general-purpose A/D input port. Since the touch panel control circuit and the A/D converter
(conversion precision: 10 bits) are both incorporated, the touch panel is connected directly to the V
R
4181.
The PIU’s function, namely the detection of X and Y coordinates, is performed partly by hardware and partly by
software.
Hardware tasks: Touch panel applied voltage control
Reception of coordinate data
Software task:
Processing of coordinate data based on data sampled by hardware
Features of the PIU’s hardware tasks are described below.
Can be directly connected to touch panel with four-pin resistance layers (on-chip touch panel driver)
Interface for on-chip A/D converter
Voltage detection at three general-purpose A/D ports and one audio input port
Operation of A/D converter based on various settings and control of voltage applied to touch panel
Sampling of X-coordinate and Y-coordinate data
Variable coordinate data sampling interval
Interrupt is triggered if pen touch occurs regardless of CPU operation mode (interrupts do not occur during
Hibernate mode)
Four dedicated buffers with up to two pages each for coordinate data
Four buffers for A/D port scan
Auto/manual options for coordinate data sampling start/stop control
Caution No clocks are supplied to the PIU, A/D converter, and D/A converter in the initial state. When
using the PIU, set the MSKPIUPCLK, MSKADUPCLK, and MSKADU18M bits of the CMUCLKMSK
register in the MBA Host Bridge to 1 in advance so that clocks are supplied.