The system oscillator (SYSOSC) is an
on-chip, accurate high frequency clock source (32MHz factory-trimmed). The SYSOSC
provides a flexible high-speed clock source to the system in cases where the crystal
oscillator (XTAL) is either not present or not used, or where fast wake-up from a
low-power mode is required.
Key features of the SYSOSC
include:
- High accuracy when using optional
frequency correction loop (FCL) and reference resistor
- The frequency correction
loop supports correction through an internal resistor
- Fast start-up time from a low
power state
- Capable of switching from base
frequency to low frequency, or low frequency to base frequency, in one clock
cycle with no functional interruption (gear shift)
- Glitch-less divider and
phase-aligned transition to minimize disturbance to peripherals
- Fast settling to
specified accuracy
- SYSCTL can initiate
seamless gear shift frequency switch in STOP mode with user-configurable
FCL enablement to reduce SYSOSC current
- Two frequency options: 32MHz
supporting RUN/SLEEP power modes and 4MHz in STOP mode
- While in 32MHz mode, a
divider giving a fixed 4MHz output can be multiplexed to when the mode
switches
The SYSOSC is active at the device's
base frequency (32MHz) by default after a brownout reset, sourcing MCLK.