C8051F340 Datasheet, PDF (141/282 Pages) List of Unclassifed Manufacturers – Full Speed USB Flash MCU Family

C8051F340/1/2/3/4/5/6/7
SFR Definition 14.4. OSCXCN: External Oscillator Control
R
R/W
R/W
R/W
R
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0 -
Bit7
Bit6
Bit5
Bit4
Bit3
R/W
XFCN2
Bit2
R/W
XFCN1
Bit1
R/W
XFCN0
Bit0
Reset Value
00000000
SFR Address:
0xB1
Bit7:
Bits6–4:
Bit3:
Bits2–0:
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.
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 = 0, Write = don't care.
XFCN2–0: External Oscillator Frequency Control Bits.
000-111: See table below:
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x)
000
f ≤ 32 kHz
f ≤ 25 kHz
001
32 kHz < f ≤ 84kHz
25 kHz < f ≤ 50 kHz
010 84 kHz < f ≤ 225 kHz 50 kHz < f ≤ 100 kHz
011 225 kHz < f ≤ 590 kHz 100 kHz < f ≤ 200 kHz
100 590 kHz < f ≤ 1.5 MHz 200 kHz < f ≤ 400 kHz
101 1.5 MHz < f ≤ 4 MHz 400 kHz < f ≤ 800 kHz
110 4 MHz < f ≤ 10 MHz 800 kHz < f ≤ 1.6 MHz
111 10 MHz < f ≤ 30 MHz 1.6 MHz < f ≤ 3.2 MHz
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
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:
f = 1.23(10³) / (R x C), where
f = frequency of clock in MHz
C = capacitor value in pF
R = Pull-up resistor value in kΩ
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), where
f = frequency of clock in MHz
C = capacitor value the XTAL2 pin in pF
V_DD = Power Supply on MCU in volts
Rev. 0.5
141