C8051F709-GQR Silicon Labs, C8051F709-GQR Datasheet - Page 171

• Manufacturer Part Number: C8051F709-GQR
• Description: 8-bit Microcontrollers - MCU 8kB 32B EEPROM Cap Sense
• Manufacturer: Silicon Labs

Specifications of C8051F709-GQR

• Rohs: yes
• Core: 8051
• Processor Series: C8051
• Data Bus Width: 8 bit

27. Oscillators and Clock Selection
C8051F70x/71x devices include a programmable internal high-frequency oscillator and an external oscilla-
tor drive circuit. The internal high-frequency oscillator can be enabled/disabled and calibrated using the
OSCICN and OSCICL registers, as shown in Figure 27.1. The system clock can be sourced by the exter-
nal oscillator circuit or the internal oscillator (default). The internal oscillator offers a selectable post-scaling
feature, which is initially set to divide the clock by 8.
27.1. System Clock Selection
The system clock source for the MCU can be selected using the CLKSEL register. The clock selected as
the system clock can be divided by 1, 2, 4, 8, 16, 32, 64, or 128. When switching between two clock divide
values, the transition may take up to 128 cycles of the undivided clock source. The CLKRDY flag can be
polled to determine when the new clock divide value has been applied. The clock divider must be set to
"divide by 1" when entering Suspend mode. The system clock source may also be switched on-the-fly. The
switchover takes effect after one clock period of the slower oscillator.
Option 4 – CMOS Mode
Option 1 – Crystal Mode
Option 3 – C Mode
Option 2 – RC Mode
XTAL2
VDD
XTAL2
XTAL2
10M
XTAL1
XTAL2
Figure 27.1. Oscillator Options
OSCICL
Circuit
Input
Programmable
Internal Clock
Generator
OSCXCN
Rev. 1.0
OSC
EN
OSCICN
Clock Divider
n
C8051F70x/71x
CLKSEL
Clock Divider
n
CLKRDY
SYSCLK
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