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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Operating Modes and System Clocks
Operating Modes and System Clocks
High Speed Oscillator Control Register – HSOCR
SFR Address: EFh
Bit
7
6
5
4
3
2
1
0
Name
—
—
HXTRDY HIRCRDY
—
—
HXTEN
HIRCEN
R/W
—
—
R
R
—
—
R/W
R/W
POR
—
—
0
1
—
—
0
1
Bit 7~6
Unimplemented, read as “0”
Bit 5
HXTRDY:
HXT oscillator ready indication bit
0: Not ready
1: Ready
This is the external high frequency oscillator, HXT, ready indication bit which indicates
if the HXT oscillator is stable or not. This bit will be cleared to zero by hardware when
the device is powered on. After power on, if the HXT oscillator is selected, the bit will
change to a high level when the external high frequency oscillator is stable.
Bit 4
HIRCRDY:
HIRC oscillator ready indication bit
0: Not ready
1: Ready
This is the internal high frequency oscillator, HIRC, ready indication bit which indicates
if the HIRC oscillator is stable or not. This bit will be cleared to zero by hardware when
the HIRC function is disabled. After power on, if the HIRC oscillator is enabled, the bit
will change to a high level when the internal high frequency oscillator is stable.
Bit 3~2
Unimplemented, read as “0”
Bit 1
HXTEN:
HXT control bit
0: Disable
1: Enable
Bit 0
HIRCEN:
HIRC control bit
0: Disable
1: Enable
After power on, this bit will be set high thus selecting the HIRC as the initial system
oscillator.
Low Speed Oscillator Control Register – LSOCR
SFR Address: EEh
Bit
7
6
5
4
3
2
1
0
Name
—
—
—
LSORDY
—
—
LSOSEL
—
R/W
—
—
—
R
—
—
R/W
—
POR
—
—
—
1
—
—
0
—
Bit 7~5
Unimplemented, read as “0”
Bit 4
LSORDY:
Low speed oscillator ready indication flag
0: Not ready
1: Ready
This is the common ready flag for the two low speed oscillators, LIRC and LXT,
which indicates if the low speed oscillator is stable or not. During low speed oscillator
switching this bit will be automatically cleared to zero by the hardware.
Bit 3~2
Unimplemented, read as “0”
Bit 1
LSOSEL:
Low frequency oscillator select bit
0: LIRC
1: LXT
Bit 0
Unimplemented, read as “0”