
Rev. 1.20
44
November 20, 2019
Rev. 1.20
45
November 20, 2019
HT66F2740
12V High Current Flash MCU
HT66F2740
12V High Current Flash MCU
• SCC Register
Bit
7
6
5
4
3
2
1
0
Name
CKS2
CKS1
CKS0
—
—
—
FHIDEN FSIDEN
R/W
R/W
R/W
R/W
—
—
—
R/W
R/W
POR
0
0
1
—
—
—
0
0
Bit 7~5
CKS2~CKS0
: System clock selection
000: f
H
001: f
H
/2
010: f
H
/4
011: f
H
/8
100: f
H
/16
101: f
H
/32
110: f
H
/64
111: f
SUB
These three bits are used to select which clock is used as the system clock source. In
addition to the system clock source directly derived from f
H
or f
SUB
, a divided version
of the high speed system oscillator can also be chosen as the system clock source.
Bit 4~2
Unimplemented, read as “0”
Bit 1
FHIDEN
: High Frequency oscillator control when CPU is switched off
0: Disable
1: Enable
This bit is used to control whether the high speed oscillator is activated or stopped
when the CPU is switched off by executing an “HALT” instruction.
Bit 0
FSIDEN
: Low Frequency oscillator control when CPU is switched off
0: Disable
1: Enable
This bit is used to control whether the low speed oscillator is activated or stopped
when the CPU is switched off by executing an “HALT” instruction.
• HIRCC Register
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
—
HIRC1
HIRC0
HIRCF
HIRCEN
R/W
—
—
—
—
R/W
R/W
R
R/W
POR
—
—
—
—
0
0
0
1
Bit 7~4
Unimplemented, read as “0”
Bit 3~2
HIRC1~HIRC0
: HIRC frequency selection
00: 8MHz
01: 12MHz
10: 16MHz
11: 8MHz
When the HIRC oscillator is enabled or the HIRC frequency selection is changed
by application program, the clock frequency will automatically be changed after the
HIRCF flag is set high.
It is recommended that the HIRC frequency selected by these two bits should be the
same with the frequency determined by the configuration option to achieve the HIRC
frequency accuracy specified in the A.C. Characteristics.
Bit 1
HIRCF
: HIRC oscillator stable flag
0: HIRC unstable
1: HIRC stable
This bit is used to indicate whether the HIRC oscillator is stable or not. When the
HIRCEN bit is set high to enable the HIRC oscillator or the HIRC frequency selection
is changed by application program, the HIRCF bit will first be cleared to zero and then
set high after the HIRC oscillator is stable.