Silicon Laboratories C8051F346 Two-Way Radio User Manual


 
Rev. 0.5 135
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.
Figure 14.1. Oscillator Diagram
Clock Multiplier
OSC
Input
Circuit
XTLVLD
XTAL1
XTAL2
Option 2
VDD
XTAL2
Option 1
10M
Option 3
XTAL2
Option 4
XTAL2
OSCXCN
XTLVLD
XOSCMD2
XOSCMD1
XOSCMD0
XFCN2
XFCN1
XFCN0
CLKMUL
MULEN
MULINIT
MULRDY
MULSEL1
MULSEL0
Programmable High-
Frequency Oscillator
EN
OSCICL OSCICN
IOSCEN
IFRDY
SUSPEND
IFCN1
IFCN0
EXOSC / 2
x 2 x 2EXOSC
IOSC
SYSCLK
EXOSC
EXOSC / 2
EXOSC / 3
EXOSC / 4
IOSC / 2
USBCLK
USBCLK2-0
CLKSEL
USBCLK2
USBCLK1
USBCLK0
CLKSL2
CLKSL1
CLKSL0
IOSC
Programmable Low-
Frequency Oscillator
(C8051F340/1/2/3/4/5)
EN
EXOSC
OSCLCN
OSCLEN
OSCLRDY
OSCLF3
OSCLF2
OSCLF1
OSCLF0
OSCLD1
OSCLD0
n
n
OSCLF3-0