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51.6.6 Low-Power Channel Threshold register (TSIx_THRESHOLD)
Address: 4004_5000h base + 120h offset = 4004_5120h
Bit 31 30 29 28 27 26 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 0
R
LTHH HTHH
W
Reset
0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
TSIx_THRESHOLD field descriptions
Field Description
31–16
LTHH
Touch Sensing Channel Low Threshold Value
15–0
HTHH
Touch Sensing Channel High Threshold Value
51.7 Functional description
This section provides functional description of the TSI module.
51.7.1 Capacitance measurement
The electrode pin capacitance measurement uses a dual oscillator approach. The TSI
electrode oscillator has its frequency dependable of the external electrode capacitance
and of the TSI module configuration. After going to a configurable prescaler, the TSI
electrode oscillator signal goes to the input of the module counter. The time for the
module counter to reach its module value is measured using the TSI reference oscillator.
The measured electrode capacitance is directly proportional to the time.
Chapter 51 Touch sense input (TSI)
K20 Sub-Family Reference Manual, Rev. 1.1, Dec 2012
Freescale Semiconductor, Inc.
Preliminary
1427
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