C8051F310 Datasheet, PDF (117/224 Pages) List of Unclassifed Manufacturers – 8/16 kB ISP Flash MCU Family

C8051F310/1/2/3/4/5/6/7
12. Oscillators
C8051F31x 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 registers, as
shown in Figure 12.1. The system clock can be sourced by the external oscillator circuit, the internal oscil-
lator, or a scaled version of the internal oscillator. The internal oscillator's electrical specifications are given
in Table 12.1 on page 119.
Option 3
XTAL2
OSCICL
OSCICN
CLKSEL
Option 4
XTAL2
EN
Programmable
n
Internal Clock
Generator
Option 2
VDD
XTAL2
Option 1
XTAL1
10MΩ
XTAL2
Input
Circuit
OSC
SYSCLK
OSCXCN
Figure 12.1. Oscillator Diagram
12.1. Programmable Internal Oscillator
All C8051F31x devices include a programmable internal oscillator that defaults as the system clock after a
system reset. The internal oscillator period can be programmed via the OSCICL register as defined by
SFR Definition 12.1 OSCICL is factor calibrated to obtain a 24.5 MHz frequency.
Electrical specifications for the precision internal oscillator are given in Table 12.1 on page 119. 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 register OSCICN. The divide value defaults to 8 following a reset.
Rev. 1.6
117