C8051F007 View Datasheet(PDF) - Silicon Laboratories

Part Name

Description

MFG CO.

C8051F007

Mixed-Signal 32KB ISP FLASH MCU Family

Silicon Laboratories 

C8051F000/1/2/5/6/7

C8051F010/1/2/5/6/7

14. OSCILLATOR

Each MCU includes an internal oscillator and an external oscillator drive circuit, either of which can generate the

system clock. The MCUs boot from the internal oscillator after any reset. The internal oscillator starts up instantly.

It can be enabled/disabled and its frequency can be changed using the Internal Oscillator Control Register

(OSCICN) as shown in Figure 14.2. The internal oscillator’s electrical specifications are given in Table 14.1.

Both oscillators are disabled when the /RST pin is held low. The MCUs can run from the internal oscillator or

external oscillator, and switch between the two at will using the CLKSL bit in the OSCICN Register. The external

oscillator requires an external resonator, parallel-mode crystal, capacitor, or RC network connected to the

XTAL1/XTAL2 pins (see Figure 14.1). The oscillator circuit must be configured for one of these sources in the

OSCXCN register. An external CMOS clock can also provide the system clock via overdriving the XTAL1 pin.

The XTAL1 and XTAL2 pins are 3.6V (not 5V) tolerant. The external oscillator can be left enabled and running

even when the MCU has switched to using the internal oscillator.

Figure 14.1. Oscillator Diagram

OSCICN

opt. 4

XTAL1

opt. 3

XTAL1

XTAL2

opt. 2

AV+

XTAL1

opt. 1

XTAL1

XTAL2

VDD

EN

Internal Clock

Generator

AV+

Input

Circuit

OSC

AGND

OSCXCN

SYSCLK

99

Rev. 1.7

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