Silicon Laboratories Stepper Machine Especificações descarregar pdf (Página 110)

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

) / (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

1 2 ... 105 106 107 108 109 110 111 112 113 114 115 ... 203 204

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