Information

48.7.3.4.1 Active mode periodic scan
In active mode periodic scan the scan following clocks can be selected: LPOOSCCLK,
MCGIRCLK and OSCERCLK. The bit field SCANC[AMCLKS] selects the TSI clock
source for the active mode scan. The scan period is determined by the SCANC[SMOD]
value. SMOD is the module of the counter that determines the scan period.
The following figure presents the scan sequence performed by the TSI module. Every
active electrode is scanned sequentially, stating with the TSI_IN[0] and ending with the
TSI_IN[15] pin, if they are active.
When the electrode scan unit starts a scan sequence, all the active electrodes will be
scanned sequentially with each electrode has the scanned time defined by the
GENCS[NSCN]. The counter value is the sum of the total scan times of that electrode.
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Scan
States
Result
Counter
End-of-Scan
Signal
Count from 0 to result
Count from 0 to result Count from 0 to result
1st Scan
1st Scan
Last Scan
Last Scan
Last Scan
1st Scan
First Active
Electrode
Second Active
Electrode
Last Active
Electrode
Figure 48-41. Scan sequence
48.7.3.4.2 Low power mode scan
In low power periodic scan the scan period is define by the GENCS[LPSCNITV]. The
TSI module is only enabled in low power modes only if the bit GENCS[STPE] is 1.
Only one electrode pin is functional in the low power mode scan and it’s defined by the
bit-field PEN[LPSP].
48.7.3.4.3 End-of-scan interrupt
The electrode scan unit sets the EOSF flag in the GENCS registers once all the active
electrode scan finishes. The EOSF Flag generate an end-of-scan interrupt request if it is
enabled.. The interrupt is asserted if enabled by GENCS[TSIIE] and GENCS[ESOR] bits.
Functional descriptions
K20 Sub-Family Reference Manual, Rev. 2, Feb 2012
1210 Freescale Semiconductor, Inc.