42.4.5 Scan timesThe TSI provides multi-scan function. The number of scans is indicated by theTSI_GENCS[NSCN] bits that allow the scan number from 1 to 32. WhenTSI_GENCS[NSCN] is set to 0 (only once), the single scan is engaged. The 16-bitcounter accumulates all scan results until the NSCN time scan completes, and users canread TSI_DATA[TSICNT] to get this accumulation. When DMA transfer is enabled, thecounter values can also be read out by DMA engine.42.4.6 Clock settingTSI is built with dual oscillator architecture. In normal sensing application, the referenceoscillator clock is the only clock source for operations. The reference clock is used tomeasure the electrode oscillator by ticking a 16-bit counter. The reference oscillatorfrequency depends on the current source setting. Please refer to the Current source formore details.The output of electrode oscillator has several prescalers up to 128 indicated byTSI_GENCS[PS]bits. This allows a flexible counter configuration for different electrodeoscillator frequency.42.4.7 Reference voltageThe TSI module offers a internal reference voltage for both electrode oscillator andreference oscillator. The internal reference voltage can work in low power modes evenwhen the MCU regulator is partially powered down, which is ideally for low-power touchdetection.The charge and discharge difference voltage is configurable upon the setting ofTSI_GENCS[DVOLT] bits. The following table shows the all the delta voltageconfigurations.Note this table doesn't apply to noise mode, where the details should beconsult form noise modes chapters.Table 42-11. Delta voltage configurationDVOLT Vp (V) Vm (V) ΔV (V)00 1.328 0.302 1.02601 1.111 0.519 0.59210 0.986 0.644 0.34211 0.914 0.716 0.198Functional descriptionKL25 Sub-Family Reference Manual, Rev. 3, September 2012798 Freescale Semiconductor, Inc.
