mcf51jf128 Freescale Semiconductor, Inc, mcf51jf128 Datasheet - Page 1236

• Manufacturer Part Number: mcf51jf128
• Description: Mcf51jf128 Reference Manual
• Manufacturer: Freescale Semiconductor, Inc

Functional descriptions
Once an electrode scan is triggered, the electrode scan unit controls the scanning of all
the active electrodes sequentially. It starts the scanning of the electrode pin TSI_IN[0]
and goes sequentially scanning until it reaches the electrode pin TSI_IN[15]. The
electrode pin that does not have its bit (PEN[PEN]) enabled is not scanned and is
skipped.
Only one electrode pin is functional in the low power mode scan and it’s defined by the
PEN[LPSP]. In low power scan mode, the configuration of PEN[PEN] bits is ignored.
48.7.3.2 Scan trigger
The scan trigger can be set to periodical scan or software trigger. The bit GENCS[STM]
determines the TSI scan trigger mode. If STM = 1 the trigger mode is selected as
continuous. If STM = 0, the software trigger mode is selected. In periodic mode the scan
trigger is generated automatically by the electrode scan unit.
48.7.3.3 Software trigger mode
The software trigger scan is started by writing 1 to the bit GENCS[SWTS]. A single scan
of all active electrodes is performed. The software trigger scan only can be initiated by
the GENCS[SWTS] bit if the STM = 0. If STM = 1, any write in the GENCS[SWTS] bit
is ignored.
48.7.3.4 Periodic scan control
The electrode scan unit operates both in TSI active mode and TSI low power mode. It has
a separate scan period control for each one of these modes. It allows the application to
controls the trade-off of the scan frequency and the average TSI module power
consumption.
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It takes some time (less than 40 µs) for TSI oscillators to be
stable in software trigger mode and periodical scan mode.In the
first scan process, TSI_GENCS[SCNIP] lags some time before
a valid after trigger happens.
MCF51JF128 Reference Manual, Rev. 2, 03/2011
Preliminary
NOTE
Freescale Semiconductor, Inc.