C8051F340/1/2/3/4/5/6/7

14. Oscillators

C8051F340/1/2/3/4/5/6/7 devices include a programmable internal high-frequency oscillator, a program- mable internal low-frequency oscillator (C8051F340/1/2/3/4/5), an external oscillator drive circuit, and a 4x Clock Multiplier. The internal high-frequency and low-frequency oscillators can be enabled/disabled and adjusted using the special function registers, as shown in Figure 14.1. The system clock (SYSCLK) can be derived from either of the internal oscillators, the external oscillator circuit, or the 4x Clock Multiplier divided by 2. The USB clock (USBCLK) can be derived from the internal oscillator, external oscillator, or 4x Clock Multiplier. Oscillator electrical specifications are given in Table 14.1.

Option 2

Option 3

VDD

 

XTAL2

XTAL2

 

Option 1

XTAL1

 

OSCICL

 

OSCICN

 

OSCLCN

CLKSEL

IOSCEN

IFRDY SUSPEND

IFCN1 IFCN0

OSCLEN OSCLRDY OSCLF3 OSCLF2 OSCLF1 OSCLF0 OSCLD1 OSCLD0

USBCLK2 USBCLK1 USBCLK0

CLKSL2 CLKSL1 CLKSL0

EN

 

IOSC

 

 

 

 

Programmable High-

n

 

 

 

 

 

 

 

Frequency Oscillator

 

 

 

 

 

OSCLF3-0

 

 

 

 

 

 

EN

 

 

 

n

 

 

Programmable Low-

 

 

 

 

 

Frequency Oscillator

 

 

 

 

SYSCLK

(C8051F340/1/2/3/4/5)

 

 

 

 

 

10M

XTAL2

Option 4

XTAL2

 

 

 

 

Input

OSC

 

 

 

 

 

 

 

 

Circuit

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

XTLVLD

EXOSC

 

 

IOSC

 

 

EXOSC

x 2

x 2

EXOSC / 2

 

IOSC / 2

Clock Multiplier

 

 

EXOSC

XTLVLD

XOSCMD2

XOSCMD1

XOSCMD0

 

XFCN2

XFCN1

XFCN0

 

 

 

 

 

 

 

 

OSCXCN

MULEN

MULINIT

MULRDY

 

 

 

MULSEL1

MULSEL0

 

 

 

 

 

 

 

 

CLKMUL

EXOSC / 2 EXOSC / 3 EXOSC / 4

USBCLK2-0

USBCLK

Figure 14.1. Oscillator Diagram

Rev. 0.5

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Silicon Laboratories C8051F342, C8051F347, C8051F346, C8051F341, C8051F343, C8051F340 Oscillators, Oscillator Diagram