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Rev. 1.00
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Standard 8051 8-Bit Flash MCU
HT85F2260/HT85F2270/HT85F2280
Operating Modes and System Clocks
Operating Modes and System Clocks
PLL Control Register – PLLCR
SFR Address: EDh
Bit
7
6
5
4
3
2
1
0
Name
PLLEN
PLLRDY
—
PLLSRC
—
PLLM�
PLLM1
PLLM0
R/W
R/W
R
—
R/W
—
R/W
R/W
R/W
POR
0
0
—
0
—
0
0
0
Bit 7
PLLEN:
PLL enable/disable control
0: PLL disable
1: PLL enable
Bit 6
PLLRDY:
PLL output ready indication flag
0: Not ready
1: Ready
After the PLL is enabled this bit is used to indicate when the PLL is locked and ready
for use. This bit will be initially cleared to zero by hardware when the device is powered
on. The bit will be cleared to zero if the PLL is in use and is then disabled but will not
be cleared if the PLL changes frequency.
Bit 5
Unimplemented, read as “0”
Bit 4
PLLSRC:
PLL Clock Source Select
0: HIRC clock source
1: HXT clock source
Note that if the PLL clock source is selected to be the external oscillator, HXT, the
crystal frequency should be 4MHz.
Bit 3
Unimplemented, read as “0”
Bit 2~0
PLLM2,
PLLM1, PLLM0:
PLL Frequency Multiplier select
000: ×1
001: ×2
010: ×3
011: ×4
100: ×5
101: ×6
110: ×7
111: ×8