C8051F340_0608 Datasheet, PDF (148/288 Pages) Silicon Laboratories – Full Speed USB Flash MCU Family

C8051F340/1/2/3/4/5/6/7
SFR Definition 14.6. CLKSEL: Clock Select
R/W
R/W
R/W
R/W
R/W
R/W
R/W
R/W Reset Value
-
USBCLK
-
CLKSL
00000000
Bit7
Bit6
Bit5
Bit4
Bit3
Bit2
Bit1
Bit0 SFR Address
0xA9
Bit 7:
Bits6–4:
Unused. Read = 0b; Write = don’t care.
USBCLK2–0: USB Clock Select
These bits select the clock supplied to USB0. When operating USB0 in full-speed mode, the
selected clock should be 48 MHz. When operating USB0 in low-speed mode, the selected
clock should be 6 MHz.
USBCLK
000
001
010
011
100
101
110
111
Selected Clock
4x Clock Multiplier
Internal Oscillator / 2
External Oscillator
External Oscillator / 2
External Oscillator / 3
External Oscillator / 4
RESERVED
RESERVED
Bit3: Unused. Read = 0b; Write = don’t care.
Bits2–0: CLKSL2–0: System Clock SelectThese bits select the system clock source.
CLKSL
000
Selected Clock
Internal Oscillator (as determined by the
IFCN bits in register OSCICN)
001
External Oscillator
010
011*
100
101-111
4x Clock Multiplier / 2
4x Clock Multiplier*
Low-Frequency Oscillator
RESERVED
*Note: This option is only available on 48 MHz devices
148
Rev. 1.0