Holtek BS83A04C Manual Download Page 76

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Rev. 1.00

March 24, 2020

Rev. 1.00

March 24, 2020

BS83A04C

4-Key Enhanced Touch I/O Flash MCU

BS83A04C

4-Key Enhanced Touch I/O Flash MCU

In the periodic auto scan mode the touch key scan operation will be implemented automatically on
a periodic basis, which can be determined by the ASMP1~ASMP0 bits in the TKC2 register. The
number of touch key scan times depends upon the WDT time-out period and the periodic auto scan

mode period. Each auto scan operation will sequentially be carried out in a specific way from time

slot 0 to time slot 3 like the auto scan mode. The reference oscillator internal capacitor value for each
time slot selected key will be read from the touch key data memory and loaded into the TKM0ROH/
TKM0ROL registers. However, only at the end of the last scan operation in the WDT time-out cycle,
the 16-bit C/F counter value for all scanned keys will be written into the corresponding touch key
data memory.
In addition, the 16 bit upper/lower threshold value for the selected key to be scanned in the time slot

0 will be read from a specific location of the dedicated touch key data memory and loaded into the

corresponding TKM0TH16H/TKM0TH16L registers before the selected key will start to be scanned
in time slot 0. The TKM0TH16H/TKM0TH16L register pair will be loaded with the corresponding
next time slot 16-bit upper/lower threshold value from the dedicated touch key data memory
automatically by the hardware at the end of the current time slot when the periodic auto scan mode is
selected. each touch key has its own independent upper/lower threshold comparaor. The upper/lower
threshold comparison function will automatically be enabled in the periodic auto scan mode. When
any key C/F counter value is less than the lower threshold if M0KnTHS=0, or larger than the upper

threshold if M0KnTHS=1, this indicates that the touch key state changes, then the M0KnTHF flag

will be set high by the hardware, and an interrupt signal will be generated. Note that if the touch key
threshold TKTH interrupt occurs, 1-byte data will be written to the TKM0ROL register because the
TKM0ROH/TKM0ROL register pair will be loaded with the corresponding next time slot capacitor
value from the dedicated touch key data memory and the 16-bit C/F counter content, TKM016DH/
TKM016DL, and the TKM0TH16H/TKM0TH16L value are compared at the same time.
As the periodic auto scan operation is implemented using the WDT counter clock to reduce power
consumption, when the WDT is cleared the WDT counter will be reset, the periodic auto scan

operation time will be affected but the number of touch key times will not be affected.

Touch Key Data Memory

The device provides three dedicated Data Memory area. The first area is used to store the 16-bit C/

F counter values of the touch key module and located in Data Memory Sector 5, The second area is
used to store the reference oscillator internal capacitor values of the touch key module and located
in Data Memory Sector 6. The last area is used to store the 16-bit upper/lower threshold value of the
touch key module and located in Data Memory Sector 7.

10-bit Ref. OSC capacitor

16-bit C/F counter

Comparetor

Upper/Low side

threshold Register

TKTH

M0KnTHS

TKM0ROL / TKM0ROH

TKM016DL / TKM016DH

TKM0TH16H/TKM0TH16L

Note: n=Touch Key number, 1~4.

16-bit C/F counter value