Information

52.4.3 TSI low power mode
The TSI module enters low power mode if the GENCS[STPE] is set to one and the MCU
is programmed into one of the following operational modes: LLS, VLLS1, VLLS2 or
VLLS3. In low power mode, only one selectable pin is active, being able to perform
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, entrance into the active mode, and the
MCU wake up.
In low power mode the electrode scan unit is always configured to periodical low power
scan.
52.4.4 Block diagram
The following figure shows the block diagram of TSI module.
Cap Switch
PAD0
PAD1
PAD15
TSI
Electrode
Oscillator
NSCN
TSICHnCNT
Prescaler
Counter
Modulo
Control
TSI Reference Oscillator
16-bit
Counter
EXTCHRG
DELVOL PS
REFCHRG
DELVOL
Scan
Trigger
Channel
Polling
FSM
Low
Power
Scan
Control
STM STPE
SMOD
LPSCNITV
EOSF
PEN[15:0]
OVRF
overrun interrupt
end of scan interrupt
LPOCLK
VLPOSCCLK
LLS/VLLSx
Modes
BUS CLK
MCGIRCLK
OSCERCLK
Electrode Scan Unit
2 Windowed
Comparators
Touch and
Error
Detection
Error Interrupt
EXTERF
OUTRGF
out of range
interrupt
TSICHnHTH
TSICHnLTH
Touch Detection Unit
Capacitance Measurement Unit
CAPTRM
Figure 52-3. TSI block diagram
Chapter 52 Touch sense input (TSI)
K20 Sub-Family Reference Manual, Rev. 6, Nov 2011
Freescale Semiconductor, Inc. 1571