Sfr Definition 14.4. Oscxcn: External Oscillator Control - Silicon Laboratories C8051F341 Product Manual

SFR Definition 14.4. OSCXCN: External Oscillator Control

R R/W
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0
Bit7 Bit6
Bit7: 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.
Bits6–4: XOSCMD2–0: External Oscillator Mode Bits.
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.
Bit3: RESERVED. Read = 0, Write = don't care.
Bits2–0: XFCN2–0: External Oscillator Frequency Control Bits.
000-111: See table below:
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x)
000
32 kHz  f  84kHz
001
84 kHz  f  225 kHz
010
225 kHz  f  590 kHz
011
590 kHz  f  1.5 MHz
100
1.5 MHz  f  4 MHz
101
4 MHz  f  10 MHz
110
10 MHz  f  30 MHz
111
CRYSTAL MODE (Circuit from Figure 14.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match crystal or resonator frequency.
RC MODE (Circuit from Figure 14.1, Option 2; XOSCMD = 10x)
Choose XFCN value to match frequency range:
3
f = 1.23(10 ) / (R x C) , where
f = frequency of clock in MHz
C = capacitor value in pF
R = Pull-up resistor value in k 
C MODE (Circuit from Figure 14.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C x V
DD
f = frequency of clock in MHz
C = capacitor value the XTAL2 pin in pF
V = Power Supply on MCU in volts
DD
C8051F340/1/2/3/4/5/6/7/8/9/A/B/C/D
R/W R/W R
-
Bit5 Bit4 Bit3
f  32 kHz f  25 kHz
25 kHz  f  50 kHz
50 kHz  f  100 kHz
100 kHz  f  200 kHz
200 kHz  f  400 kHz
400 kHz  f  800 kHz
800 kHz  f  1.6 MHz
1.6 MHz  f  3.2 MHz
) , where
Rev. 1.3
R/W R/W R/W
XFCN2 XFCN1 XFCN0
Bit2 Bit1 Bit0
C (XOSCMD = 10x)
K Factor = 0.87
K Factor = 2.6
K Factor = 7.7
K Factor = 22
K Factor = 65
K Factor = 180
K Factor = 664
K Factor = 1590
Reset Value
00000000
SFR Address:
0xB1
137