Clocking
F5xx/F6xx Clocks (UCS)
The Unified Clock System is most flexible MSP430 clock peripheral to date. It provides an
orthogonal set of clock options – any source can drive any internal clock signal. Additionally, it
provides the hardware required to dynamically tune the DCO as needed under varying conditions.
(We’ll explain later how this works.)
UCS is available on F5xx/F6xx devices
Six independent clock sources
Low Frequency
LF XT1 32768 Hz crystal
VLO 10 kHz
REFO 32 kHz
High Frequency
HF XT14 – 32 MHz crystal
XT2 4 – 32 MHz crystal
DCO FLL calibration
FLL references (divisible, too)
LFXT1 / XT1
REFO
XT2
Orthogonal: Any source to any clock
MODOSC provided for Flash & ADC12
Clocks on demand
F5xx: Unified Clock System (UCS)
Orthogonal clock system
Any source can drive
any clock signal
2 Integrated clock sources:
REFO: 32kHz, trimmed osc.
VLO: 12kHz, ultra-low
power
DCO & FLL provide high
frequency accurate timing
MODOSC provides bullet proof
timing for Flash
Crystal pins muxed with
I/O function
F5xx: Unified Clock System
Main Features:
Any OSC can drive any system
clock (MCLK,ACLK,SMCLK)
Clock divider up to 32 for each
system clock
Control the CLK in Low Power
Modes (stopped or running) and
react to module CLK requests
OSC enable logic according
requests
Supporting the FLL as sub-
module and providing the
control registers
MODOSC as Clock source for
Flash and ADC
4 - 14 MSP430 Workshop - MSP430 Clocks & Initialization
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