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C8051F340-GQR Datasheet, PDF (137/276 Pages) Silicon Laboratories – Full Speed USB Flash MCU Family | |||
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C8051F340/1/2/3/4/5/6/7/8/9/A/B/C/D
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:
Bits6â4:
Bit3:
Bits2â0:
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.
XOSCMD2â0: 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.
XFCN2â0: External Oscillator Frequency Control Bits.
000-111: See table below:
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x)
000
f ï£ 32 kHz
f ï£ï 25 kHz
001
32 kHz ï¼ï f ï£ï 84kHz
25 kHz ï¼ï f ï£ï 50 kHz
010 84 kHz ï¼ f ï£ï 225 kHz 50 kHz ï¼ï f ï£ï 100 kHz
011 225 kHz ï¼ f ï£ï 590 kHz 100 kHz ï¼ï f ï£ï 200 kHz
100 590 kHz ï¼ f ï£ï 1.5 MHz 200 kHz ï¼ï f ï£ï 400 kHz
101 1.5 MHz ï¼ f ï£ï 4 MHz 400 kHz ï¼ï f ï£ï 800 kHz
110 4 MHz ï¼ f ï£ï 10 MHz 800 kHz ï¼ï f ï£ï 1.6 MHz
111 10 MHz ï¼ f ï£ï 30 MHz 1.6 MHz ï¼ï f ï£ï 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 kï
C MODE (Circuit from Figure 14.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C x VDD), where
f = frequency of clock in MHz
C = capacitor value the XTAL2 pin in pF
VDD = Power Supply on MCU in volts
Rev. 1.3
137
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