Specifications

C8051F330/1
110 Rev. 1.1
Figure 13.5. OSCXCN: External Oscillator Control Register
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:
CRYSTAL MODE (Circuit from Figure 13.1, Option 1; XOSCMD = 11x)
Choose XFCN value to match crystal frequency.
RC MODE (Circuit from Figure 13.1, Option 2; XOSCMD = 10x)
Choose XFCN value to match frequency range:
f = 1.23(10
3
) / (R * 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 13.1, Option 3; XOSCMD = 10x)
Choose K Factor (KF) for the oscillation frequency desired:
f = KF / (C * VDD), where
f = frequency of clock in MHz
C = capacitor value the XTAL2 pin in pF
VDD = Power Supply on MCU in volts
R R/W R/W R/W R R/W R/W R/W Reset Value
XTLVLD XOSCMD2 XOSCMD1 XOSCMD0 - XFCN2 XFCN1 XFCN0 00000000
Bit7 Bit6 Bit5 Bit4 Bit3 Bit2 Bit1 Bit0 SFR Address:
0xB1
XFCN Crystal (XOSCMD = 11x) RC (XOSCMD = 10x) C (XOSCMD = 10x)
000 f ≤ 32kHz f ≤ 25kHz K Factor = 0.87
001 32kHz < f ≤ 84kHz 25kHz < f ≤ 50kHz K Factor = 2.6
010 84kHz < f ≤ 225kHz 50kHz < f ≤ 100kHz K Factor = 7.7
011 225kHz < f ≤ 590kHz 100kHz < f ≤ 200kHz K Factor = 22
100 590kHz < f ≤ 1.5MHz 200kHz < f ≤ 400kHz K Factor = 65
101 1.5MHz < f ≤ 4MHz 400kHz < f ≤ 800kHz K Factor = 180
110 4MHz < f ≤ 10MHz 800kHz < f ≤ 1.6MHz K Factor = 664
111 10MHz < f ≤ 30MHz 1.6MHz < f ≤ 3.2MHz K Factor = 1590