C8051F326 Datasheet, PDF (73/140 Pages) List of Unclassifed Manufacturers – Full Speed USB, 16 kB Flash MCU Family

C8051F326/7
10. Oscillators
C8051F326/7 devices include a programmable internal oscillator, an external clock input circuit, a low fre-
quency internal oscillator, and a 4x Clock Multiplier. The internal oscillator can be enabled/disabled and
calibrated using the OSCICN and OSCICL registers, as shown in Figure 10.1. The Low Frequency oscilla-
tor can be enabled/disabled and calibrated using the OSCLCN register, as shown in Figure 10.3. The sys-
tem clock (SYSCLK) can be derived from the internal oscillator, external clock, low frequency oscillator, or
the 4x Clock Multiplier divided by 2. The USB clock (USBCLK) can be derived from the internal oscillator
divided by 2, external clock, or 4x Clock Multiplier. Oscillator electrical specifications are given in
Table 10.3 on page 80.
OSCICL
OSCICN
OSCLCN
CLKSEL
CMOS
Clock
XTAL2
EN
Programmable ^IOSC
Internal Clock
n
Generator
OSCLF
EN
Low Frequency
Oscillator
Input
Circuit
EXOSC
IOSC
EXOSC
x2
x2
Clock Multiplier
IOSC / 2
EXOSC
OFF (0 Hz)
CLKMUL
SYSCLK
USBCLK
Figure 10.1. Oscillator Diagram
10.1. Programmable Internal Oscillator
All C8051F326/7 devices include a programmable internal oscillator that defaults as the system clock after
a system reset. The internal oscillator period can be adjusted via the OSCICL register. On C8051F326/7
devices, OSCICL is factory calibrated to obtain a 12 MHz frequency. Electrical specifications for the preci-
sion internal oscillator are given in Table 10.3 on page 80. 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. 0.5
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