C8051F54X_14 Datasheet, PDF (143/275 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F54x
SFR Definition 17.6. OSCXCN: External Oscillator Control
Bit
7
6
5
4
3
2
1
0
Name XTLVLD
XOSCMD[2:0]
XFCN[2:0]
Type
R
R/W
R
R/W
Reset
0
0
0
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 f  32 kHz
f 25 kHz
K Factor = 0.87
001 32 kHz f 84 kHz 25 kHz f 50 kHz K Factor = 2.6
010 84 kHz  f 225 kHz 50 kHz f 100 kHz K Factor = 7.7
011 225 kHz  f 590 kHz 100 kHz f 200 kHz K Factor = 22
100 590 kHz  f 1.5 MHz 200 kHz f 400 kHz K Factor = 65
101 1.5 MHz  f 4 MHz 400 kHz f 800 kHz K Factor = 180
110 4 MHz  f 10 MHz 800 kHz f 1.6 MHz K Factor = 664
111 10 MHz  f 30 MHz 1.6 MHz f 3.2 MHz K Factor = 1590
Rev. 1.1
143