Rev. 1.00
72
March 24, 2020
Rev. 1.00
73
March 24, 2020
BS83A04C
4-Key Enhanced Touch I/O Flash MCU
BS83A04C
4-Key Enhanced Touch I/O Flash MCU
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.
TKST
M0KOEN
M0ROEN
KEY OSC CLK
Reference OSC CLK
f
CFTMCK
Enable
f
CFTMCK
(M0DFEN=0)
f
CFTMCK
(M0DFEN=1)
TKBUSY
TKRCOV
Cleared by hardware
Set Touch Key TKRCOV interrupt request flag
8-bit time slot counter overflow time
Touch Key Manual Scan Mode Timing Diagram
The touch key module 0 contains four touch key inputs, namely KEY1~KEY4, which are shared
with logical I/O pins, and the desired function is selected using register bits. The touch key has its
own independent sense oscillator. There are therefore four sense oscillators within the touch key
module 0.
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 TKRCOV interrupt signal
will be generated in the manual scan mode.
The touch key module 0 16-bit C/F counter, 16-bit counter, 5-bit time slot unit period counter
in the module will be automatically cleared when the TKST 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 the
TKST bit changes from low to high, the 16-bit C/F counter, 16-bit counter, 5-bit time slot unit period
counter and 8-bit time slot timer counter will be automatically switched on.