C8051F388 Datasheet, PDF (146/285 Pages) –

C8051F388/9/A/B
SFR Definition 19.6. OSCXCN: External Oscillator Control
Bit
7
6
5
4
3
2
1
0
Name XCLKVLD
XOSCMD[2:0]
XFCN[2:0]
Type
R
R/W
R
R/W
Reset
0
0
0
0
0
0
0
0
SFR Address = 0xB1; SFR Page = All Pages
Bit
Name
Function
7 XCLKVLD External Oscillator Valid Flag.
Provides External Oscillator status and is valid at all times for all modes of opera-
tion except External CMOS Clock Mode and External CMOS Clock Mode with
divide by 2. In these modes, XCLKVLD always returns 0.
0: External Oscillator is unused or not yet stable.
1: External Oscillator is running and stable.
6:4 XOSCMD[2:0] External Oscillator Mode Select.
00x: External Oscillator circuit off.
010: External CMOS Clock Mode.
011: External CMOS Clock Mode with divide-by-2 stage.
100: RC Oscillator Mode with divide-by-2 stage.
101: Capacitor Oscillator Mode with divide-by-2 stage.
110: Crystal Oscillator Mode.
111: Crystal Oscillator Mode with divide-by-2 stage.
3
Unused Read = 0; Write = don’t care
2:0 XFCN[2:0] External Oscillator Frequency Control Bits.
Set according to the desired frequency for RC mode.
Set according to the desired K Factor for C mode.
XFCN
Crystal Mode
RC Mode
C Mode
000
f 20 kHz
f 25 kHz
K Factor = 0.87
001 20 kHz f 58 kHz 25 kHz f 50 kHz
K Factor = 2.6
010 58 kHz f 155 kHz 50 kHz f 100 kHz
K Factor = 7.7
011 155 kHz f 415 kHz 100 kHz f 200 kHz
K Factor = 22
100 415 kHz f 1.1 MHz 200 kHz f 400 kHz
K Factor = 65
101 1.1 MHz f 3.1 MHz 400 kHz f 800 kHz
K Factor = 180
110 3.1 MHz f 8.2 MHz 800 kHz f 1.6 MHz
K Factor = 664
111 8.2 MHz f 25 MHz 1.6 MHz f 3.2 MHz K Factor = 1590
146
Rev. 1.1