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.