Information

The GENCS[EOSF] indicates that all active electrode scans are finished and the
respective capacitance results are in the TSICHnCNT registers. The GENCS[EOSF] is
cleared by writing one to it.
48.7.3.4.4 Over-run interrupt
If an electrode scan is in progress and there is a scan trigger the electrode scan unit
generates and over-run error by asserting the GENCS[OVRF]. If the TSI error interrupt is
active by setting the GENCS[ERIE] bit a interrupt request is asserted. The OVRF flag is
cleared by writing 1 to it.
48.7.4 Touch detection unit
The touch detection unit is responsible to detect electrode capacitance changes while in
low power mode.
It also detects the occurrence of error with the electrode in the case it capacitance result is
0x0000 or 0xFFFF. The errors can be cause by electrode pin short circuit to V
DD
or V
SS
.
Or by electrode capacitances out of the configuration range of the TSI module.
48.7.4.1 Capacitance change threshold
Each TSI pin has it result register TSICHnCNT. In low power mode only one electrode
can be active, at the end of the low power active electrode conversion the touch detection
unit compares if the TSICHnCNT result value is inside a configurable range. The
comparison range is defined individually registers, TSICHHTH, the upper threshold
value and TSICHLTH, the lower threshold value. If the TSICHnCNT happens to be out
of the range defined by TSICHLTH and TSICHHTH the GENCS[OUTRGF] flag is set
indicating that a capacitance change occurred in the low power active electrode..
48.7.4.1.1 Out-of-range interrupt
The GENCS[OUTRGF] flag generates a TSI interrupt request if the GENCS[TSIIE] bit
is set and GENCS[ESOR] bit is cleared. With this configuration, after the end-of-
electrode scan, the TSI interrupt is only requested if there is a capacitance change. If the
low power electrode capacitance does not vary, the TSI Interrupt do not interrupt the
CPU.
Chapter 48 Touch sense input (TSI)
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
Freescale Semiconductor, Inc. 1211