C8051F336/7/8/9
19. Oscillators and Clock Selection
C8051F336/7/8/9 devices include a programmable internal high-frequency oscillator, a programmable
internal low-frequency oscillator, and an external oscillator drive circuit. The internal high-frequency oscilla-
tor can be enabled/disabled and calibrated using the OSCICN and OSCICL registers, as shown in
OSCLCN register. The system clock can be sourced by the external oscillator circuit or either internal oscil-
lator. Both internal oscillators offer a selectable post-scaling feature.
OSCICL
IOSCEN
IFRDY
OSCICN
IFCN1
IFCN0
OSCLCN
OSCLEN
OSCLRDY
OSCLF3
OSCLF2
OSCLF1
OSCLF0
OSCLD1
OSCLD0
OSCLF OSCLD
SYSCLK
n
Option 3
XTAL2
Programmable
Internal Clock
Generator
OSCLF
EN
EN
n
Option 4
XTAL2
Option 2
VDD
Option 1
XTAL1
XTAL2
10MΩ
XTAL2
Low Frequency
Oscillator
OSCLD
Input
Circuit
OSC
XTLVLD
XOSCMD2
XOSCMD1
XOSCMD0
XFCN2
XFCN1
XFCN0
OSCXCN
CLKSEL
Figure 19.1. Oscillator Options
116
Rev. 0.2
SEL1
SEL0
SILABS [ SILICON LABORATORIES ]
