C8051F360/1/2/3/4/5/6/7/8/9
SFR Definition 16.5. OSCXCN: External Oscillator Control
SFR Page:
F
SFR Address: 0xB6
R
R/W
R/W
R/W
R
R/W
R/W
XFCN1
Bit1
R/W
Reset Value
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0 Reserved XFCN2
XFCN0 00000000
Bit0
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit 7:
XTLVLD: Crystal Oscillator Valid Flag.
(Valid only when XOSCMD = 11x.)
0: Crystal Oscillator is unused or not yet stable.
1: Crystal Oscillator is running and stable.
Bits 6–4: 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.
RESERVED. Read = 0b. Write = don't care.
Bit 3:
Bits 2–0: XFCN2–0: External Oscillator Frequency Control Bits.
000-111: see table below:
XFCN
000
001
010
011
100
101
110
Crystal (XOSCMD = 11x) RC (XOSCMD = 100) C (XOSCMD = 101)
f ≤ 32 kHz
f ≤ 25 kHz
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
32 kHz < f ≤ 84 kHz
84 kHz < f ≤ 225 kHz
225 kHz < f ≤ 590 kHz
590 kHz < f ≤ 1.5 MHz
1.5 MHz < f ≤ 4 MHz
4 MHz < f ≤ 10 MHz
10 MHz < f ≤ 30 MHz
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
111
CRYSTAL MODE (Circuit from Figure 16.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match crystal frequency.
RC MODE (Circuit from Figure 16.1, Option 2; XOSCMD = 10x)
Choose XFCN value to match frequency range:
3
f = 1.23(10 )/(R * C), where
f = frequency of oscillation in MHz
C = capacitor value in pF
R = Pullup resistor value in kΩ
C MODE (Circuit from Figure 16.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF/(C * V ), where
DD
f = frequency of oscillation in MHz
C = capacitor value on XTAL1, XTAL2 pins in pF
V
= Power Supply on MCU in Volts
DD
Rev. 1.0
175
SILICON [ SILICON ]
