BS84B08A-3 Datasheet, PDF (36/123 Pages) Holtek Semiconductor Inc – A/D Type Touch Key MCU

BS84B08A-3/BS84C12A-3
A/D Type Touch Key MCU
Control Register
The SMOD register is used to control the internal clocks within the device.
SMOD Register
Bit
7
6
5
4
3
2
1
0
Name CKS2 CKS1 CKS0
—
LTO
HTO IDLEN HLCLK
R/W
R/W
R/W
R/W
—
R
R
R/W
R/W
POR
0
0
0
—
0
0
1
1
Bit 7 ~ 5
Bit 4
Bit 3
Bit 2
Bit 1
Bit 0
CKS2 ~ CKS0: The system clock selection when HLCLK is “0”
000: fSUB (fLIRC)
001: fSUB (fLIRC)
010: fH/64
011: fH/32
100: fH/16
101: fH/8
110: fH/4
111: fH/2
These three bits are used to select which clock is used as the system clock source. In
addition to the system clock source, which can be LIRC, a divided version of the high
speed system oscillator can also be chosen as the system clock source.
Unimplemented, read as 0.
LTO: LIRC System OSC SST ready flag
0: Not ready
1: Ready
This is the low speed system oscillator SST ready flag which indicates when the low
speed system oscillator is stable after power on reset or a wake-up has occurred. The
flag will change to a high level after 1~2 cycles.
HTO: HIRC System OSC SST ready flag
0: Not ready
1: Ready
This is the high speed system oscillator SST ready flag which indicates when the high
speed system oscillator is stable after a wake-up has occurred. This flag is cleared to
“0” by hardware when the device is powered on and then changes to a high level after
the high speed system oscillator is stable. Therefore this flag will always be read as “1”
by the application program after device power-on. The flag will be low when in the
SLEEP or IDLE0 Mode but after power on reset or a wake-up has occurred, the flag
will change to a high level after 15~16 clock cycles if the HIRC oscillator is used.
IDLEN: IDLE Mode Control
0: Disable
1: Enable
This is the IDLE Mode Control bit and determines what happens when the HALT
instruction is executed. If this bit is high, when a HALT instruction is executed the
device will enter the IDLE Mode. In the IDLE1 Mode the CPU will stop running
but the system clock will continue to keep the peripheral functions operational, if
FSYSON bit is high. If FSYSON bit is low, the CPU and the system clock will all stop
in IDLE0 mode. If the bit is low the device will enter the SLEEP Mode when a HALT
instruction is executed.
HLCLK: System Clock Selection
0: fH/2 ~ fH/64 or fSUB
1: fH
This bit is used to select if the fH clock or the fH/2 ~ fH/64 or fSUB clock is used as the
system clock. When the bit is high the fH clock will be selected and if low the fH/2 ~
fH/64 or fSUB clock will be selected. When system clock switches from the fH clock to
the fSUB clock and the fH clock will be automatically switched off to conserve power.
Rev. 1.00
36
May 02, 2013