C8051F50x-F51x
SFR Definition 19.6. OSCXCN: External Oscillator Control
Bit
7
6
5
4
3
2
1
0
XTLVLD
XOSCMD[2:0]
XFCN[2:0]
Name
Type
Reset
R
0
R/W
0
R
0
R/W
0
0
0
0
0
SFR Address = 0x9F; SFR Page = 0x0F;
Bit
Name
Function
7
XTLVLD
Crystal Oscillator Valid Flag.
(Read only when XOSCMD = 11x.)
0: Crystal Oscillator is unused or not yet stable.
1: Crystal Oscillator is running and stable.
6:4 XOSCMD[2:0] External Oscillator Mode Select.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode.
011: External CMOS Clock Mode with divide by 2 stage.
100: RC Oscillator Mode.
101: Capacitor Oscillator Mode.
110: Crystal Oscillator Mode.
111: Crystal Oscillator Mode with divide by 2 stage.
3
Unused
Read = 0b; Write =0b
2:0
XFCN[2:0]
External Oscillator Frequency Control Bits.
Set according to the desired frequency for Crystal or RC mode.
Set according to the desired K Factor for C mode.
XFCN Crystal Mode
RC Mode
C Mode
000
001
010
011
100
101
110
111
f 32 kHz
f 25 kHz
K Factor = 0.87
K Factor = 2.6
K Factor = 7.7
32 kHz f 84 kHz
84 kHz f 225 kHz
25 kHz f 50 kHz
50 kHz f 100 kHz
225 kHz f 590 kHz 100 kHz f 200 kHz K Factor = 22
590 kHz f 1.5 MHz 200 kHz f 400 kHz K Factor = 65
1.5 MHz f 4 MHz
4 MHz f 10 MHz
400 kHz f 800 kHz K Factor = 180
800 kHz f 1.6 MHz K Factor = 664
10 MHz f 30 MHz 1.6 MHz f 3.2 MHz K Factor = 1590
Rev. 1.1
173
SILICON [ SILICON ]
