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
Figure 19.1. The internal low-frequency oscillator can be enabled/disabled and calibrated using the
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
OSCICN
OSCLCN
Option 3
XTAL2
OSCLF OSCLD
ProgrammableEN
Internal Clock
Generator
n
n
Option 4
XTAL2
OSCLF
EN
SYSCLK
Option 2
VDD
Low Frequency
Oscillator
Option 1
OSCLD
XTAL1
XTAL2
XTAL2
Input
Circuit
10MΩ
OSC
OSCXCN
CLKSEL
Figure 19.1. Oscillator Options
116
Rev. 0.2
SILICON [ SILICON ]
