C8051F340/1/2/3/4/5/6/7
SFR Definition 14.4. OSCXCN: External Oscillator Control
R |
| R/W | R/W | R/W | R | R/W | R/W | R/W | |
XTLVLD |
| XOSCMD2 | XOSCMD1 | XOSCMD0 |
| - | XFCN2 | XFCN1 | XFCN0 |
Bit7 |
| Bit6 | Bit5 | Bit4 | Bit3 | Bit2 | Bit1 | Bit0 | |
Bit7: | XTLVLD: Crystal Oscillator Valid Flag. |
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| (Read only when XOSCMD = 11x.) |
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0:Crystal Oscillator is unused or not yet stable.
1:Crystal Oscillator is running and stable.
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. |
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Reset Value
00000000
SFR Address:
0xB1
XFCN | Crystal (XOSCMD = 11x) | RC (XOSCMD = 10x) | C (XOSCMD = 10x) |
000 | f ≤ 32 kHz | f ≤ 25 kHz | K Factor = 0.87 |
001 | 32 kHz < f ≤ 84kHz | 25 kHz < f ≤ 50 kHz | K Factor = 2.6 |
010 | 84 kHz < f ≤ 225 kHz | 50 kHz < f ≤ 100 kHz | K Factor = 7.7 |
011 | 225 kHz < f ≤ 590 kHz | 100 kHz < f ≤ 200 kHz | K Factor = 22 |
100 | 590 kHz < f ≤ 1.5 MHz | 200 kHz < f ≤ 400 kHz | K Factor = 65 |
101 | 1.5 MHz < f ≤ 4 MHz | 400 kHz < f ≤ 800 kHz | K Factor = 180 |
110 | 4 MHz < f ≤ 10 MHz | 800 kHz < f ≤ 1.6 MHz | K Factor = 664 |
111 | 10 MHz < f ≤ 30 MHz | 1.6 MHz < f ≤ 3.2 MHz | 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 =
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. 0.5 | 141 |
