Clocking
F2xx/G2xx Clocks (BCS+)
Some F2xx devices still utilized the BCS peripheral, but the later devices – as well as the “G”
series Value-Line devices – provide users with the enhanced BCS+ peripheral. You’ll find that
this clock system has additional source options. Also, the DCO (as well as some other
peripherals, such as the ADC) are calibrated during factory testing. Thus, you can get a much
higher precision DCO by utilizing the correct calibration values stored in the flash by TI.
Very Low Power/Low Frequency
Oscillator (VLO)*
4 – 20kHz (typical 12kHz)
500nA standby
0.5%/°C and 4%/Volt drift
Not in ’21x1 devices
Crystal oscillator (LFXT1)
Programmable capacitors
Failsafe OSC_Fault
Minimum pulse filter
Digitally Controlled Oscillator
(DCO)
0-to-16MHz
+ 3% tolerance
Factory calibration in Flash
MCLK
CPU
SMCLK
Peripherals
ACLK
Peripherals
16MHz
DCO
Min
. Puls
Filter
VLO
OSC
_Fault
F2xx/G2xx Basic Clock System (BCS+)
On PUC, MCLK and SMCLK are sourced
from DCOCLK at ~1.1 MHz. ACLK is sourced
from LFXT1CLK in LF mode with an internal
load capacitance of 6pF. If LFXT1 fails, ACLK
defaults to VLO.
* Not on all devices. Check the datasheet.
MSP430 Workshop - MSP430 Clocks & Initialization 4 - 13
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