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ManualsBrandsNXP SEMICONDUCTORS ManualsMicrocontrollers, Microprocessors & QuartzesEmbedded microcontroller MAPBGA 144 (13x13) 32-Bit 100 MHz I/O number 104
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electrode scan unit also allows software triggering of the electrode scans. This feature is
very useful for initialization of the touch application to detect the initial electrode
capacitances. This module generates configurable end-of-scan interrupt to indicate the
application that all electrodes were scanned. If a new electrode scan is started while the
previous one is still in progress, an overrun error flag is generated, TSI continues the
previous scan sequence and the latest trigger is ignored.
49.3.3 Touch detection unit
The touch detection unit indicates the change in the pin capacitance. This module
compares the pin capacitance value in the result register with a pre-configured low and
high threshold. If the capacitance result register value is outside the ranges defined by the
upper and lower threshold, the touch detection unit generates an out-of-range flag to
indicate a pin capacitance change.
The upper and lower threshold values are configurable allowing the application to select
the magnitude of the capacitance change to trigger the out-of-range flag. With the
threshold values programmed properly the application noise level does not cause frequent
CPU interrupts, so minimizes the CPU touch application usage. This feature also allows
the TSI to wake up the CPU from low power modes only in a capacitance change event.
49.4 Modes of operation
The TSI module has three operation modes: disabled, active mode and low power mode.
49.4.1 TSI disabled mode
When GENCS[TSIEN] is cleared, the TSI module is disabled.
49.4.2 TSI active mode
In active mode, the TSI module has its full functionality, being able to scan up to 16
electrodes. The TSI can be in active mode with the MCU in Run, Wait, VLPR, and
VLPW modes, and the TSI can run in low power mode (only one electrode scanning in
Stop, VLPS, LLS, and VLLSx modes).
Three clock sources can be selected for the TSI module in active mode: BUS_CLK,
MCGIRCLK and OSCERCLK.
Modes of operation
K10 Sub-Family Reference Manual, Rev. 6, Nov 2011
1534 Freescale Semiconductor, Inc.