C8051F300_08 Datasheet, PDF (97/179 Pages) Silicon Laboratories – Mixed Signal ISP Flash MCU Family

C8051F300/1/2/3/4/5
11. Oscillators
C8051F300/1/2/3/4/5 devices include a programmable internal oscillator and an external oscillator drive
circuit. The internal oscillator can be enabled/disabled and calibrated using the OSCICN and OSCICL reg-
isters, as shown in Figure 11.1. The system clock can be sourced by the external oscillator circuit, the
internal oscillator, or a scaled version of the internal oscillator. The internal oscillator's electrical specifica-
tions are given in Table 11.1 on page 99.
Option 3
XTAL2
OSCICL
OSCICN
Option 4
XTAL2
EN
Programmable
n
Internal Clock
Generator
Option 2
VDD
XTAL2
Option 1
XTAL1
10M
XTAL2
Input
Circuit
OSC
SYSCLK
OSCXCN
Figure 11.1. Oscillator Diagram
11.1. Programmable Internal Oscillator
All C8051F300/1/2/3/4/5 devices include a programmable internal oscillator that defaults as the system
clock after a system reset. The internal oscillator period can be adjusted via the OSCICL register as
defined by SFR Definition 11.1. On C8051F300/1 devices, OSCICL is factory calibrated to obtain a
24.5 MHz frequency. On C8051F302/3/4/5 devices, the oscillator frequency is a nominal 20 MHz and may
vary ±20% from device-to-device.
Electrical specifications for the precision internal oscillator are given in Table 11.1 on page 99. The pro-
grammed internal oscillator frequency must not exceed 25 MHz. Note that the system clock may be
derived from the programmed internal oscillator divided by 1, 2, 4, or 8, as defined by the IFCN bits in reg-
ister OSCICN. The divide value defaults to 8 following a reset.
Rev. 2.9
97