Information

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 the 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.
48.4.4 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 48-3. TSI block diagram
1. The out of range functinality present in the Touch Detection Unit is only available in low power modes.
Modes of operation
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
1190 Freescale Semiconductor, Inc.