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capacitance measurements. The scan period is defined by GENCS[LPSCNITV] . Two
low-power clock sources are available in the TSI low-power mode, LPOCLK, and
VLPOSCCLK, being selected by GENCS[LPCLKS].
In low-power mode, the TSI interrupt can also be configured as end-of-scan or out-of-
range and the GENCS[TSIIEN] must be set in order to generate these interrupts. The TSI
interrupt causes the exit of the low-power mode and entrance in the active mode, and the
MCU also wakes up.
In low-power mode, the electrode scan unit is always configured to periodical low-power
scan.
51.4.4 Block diagram
The following figure shows the block diagram of TSI module.
1
Cap Switch
PAD0
PAD1
PAD15
TSI
Electrode
Oscillator
NSCN
TSICHnCNT
Prescaler
Counter
Modulo
Control
TSI Reference Oscillator
16-bit
Counter
EXTCHRG
PS
REFCHRG
Scan
Trigger
Channel
Polling
FSM
Low
Power
Scan
Control
STM STPE
SMOD
LPSCNITV
EOSF
PEN[15:0]
OVRF
overrun interrupt
end of scan interrupt
VLPOSCCLK
LPOCLK
MCGIRCLK
OSCERCLK
Electrode Scan Unit
2 Windowed
Comparators
Touch and
Error
Detection
Error Interrupt
EXTERF
OUTRGF
out of range
interrupt
TSICHHTH
TSICHLTH
Touch Detection Unit
Capacitance Measurement Unit
Figure 51-3. TSI block diagram
1. The out-of-range functionality present in the Touch Detection Unit is available only in low-power modes.
Modes of operation
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
1416
Preliminary
Freescale Semiconductor, Inc.
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