BS86B12A-3 Datasheet, PDF (117/195 Pages) Holtek Semiconductor Inc – Touch A/D Flash MCU with LED/LCD Driver

BS86B12A-3/BS86C16A-3/BS86D20A-3
Touch A/D Flash MCU with LED/LCD Driver
Touch Key Operation
When a finger touches or is in proximity to a touch pad, the capacitance of the pad will increase.
By using this capacitance variation to change slightly the frequency of the internal sense oscillator,
touch actions can be sensed by measuring these frequency changes. Using an internal programmable
divider the reference clock is used to generate a fixed time period. By counting a number of
generated clock cycles from the sense oscillator during this fixed time period touch key actions can
be determined.
Each touch key module contains four touch key inputs which are shared logical I/O pins, and the
desired function is selected using register Bits. Each touch key has its own independent sense
oscillator. There are therefore four sense oscillators within each touch key module.
During this reference clock fixed interval, the number of clock cycles generated by the sense
oscillator is measured, and it is this value that is used to determine if a touch action has been made
or not. At the end of the fixed reference clock time interval a Touch Key interrupt signal will be
generated.
Using the TSCS Bit in the TKC0 register can select the module 0 time slot counter as the time slot
counter for all modules. All modules use the same started signal. The16-Bit C/F counter, 16-Bit
counter, 5-Bit time slot counter in all modules will be automatically cleared when this Bit is cleared
to zero, but the 8-Bit programmable time slot counter will not be cleared. The overflow time is setup
by user. When this Bit changes from low to high, the 16-Bit C/F counter, 16-Bit counter, 5-Bit time
slot counter and 8-Bit time slot timer counter will be automatically switched on.
The key oscillator and reference oscillator in all modules will be automatically stopped and the 16-
Bit C/F counter, 16-Bit counter, 5-Bit time slot counter and 8-Bit time slot timer counter will be
automatically switched off when the 5-Bit time slot counter overflows. The clock source for the time
slot counter and 8+5 Bit counter, is sourced from the reference oscillator or fSYS/4. The reference
oscillator and key oscillator will be enabled by setting the MnROEN Bit and MnKOEN Bits in the
TKMnC1 register.
When the time slot counter in all the touch key modules or in the touch key module 0 overflows,
an actual touch key interrupt will take place. The touch keys mentioned here are the keys which are
enabled.
Each touch key module consists of four touch keys, Key1 ~ Key4 are contained in module 0, Key5
~ Key8 are contained in module 1, Key9 ~ Key12 are contained in module 2, Key13 ~ Key16 are
contained in the module 3 and Key17 ~ Key20 are contained in the module 4. Each touch key
module has an identical structure.
Rev. 1.40
117
December 05, 2016