Adjusting the DCO frequency

Basic Clock Module Operation

After a PUC, the internal resistor is selected for the DC generator, RSELx = 4, and DCOx = 3, allowing the DCO to start at a mid-range frequency. MCLK and SMCLK are sourced from DCOCLK. Because the CPU executes code from MCLK, which is sourced from the fast-starting DCO, code execution begins from PUC in less than 6 ∝s. The typical DCOx and RSELx ranges and steps are shown in Figure 4−5.

The frequency of DCOCLK is set by the following functions:

-The current injected into the DC generator by either the internal or external resistor defines the fundamental frequency. The DCOR bit selects the internal or external resistor.

-The three RSELx bits select one of eight nominal frequency ranges for the DCO. These ranges are defined for an individual device in the device-specific data sheet.

-The three DCOx bits divide the DCO range selected by the RSELx bits into 8 frequency steps, separated by approximately 10%.

-The five MODx bits, switch between the frequency selected by the DCOx bits and the next higher frequency set by DCOx+1. When DCOx = 07h, the MODx bits have no effect because the DCO is already at the highest setting for the selected RSELx range.

Figure 4−5. Typical DCOx Range and RSELx Steps

fDCO

10000 kHz

1000 kHz

RSEL=7

RSEL=6

RSEL=5

RSEL=4

RSEL=3

RSEL=2

RSEL=1

RSEL=0

100 kHz

DCO=0 DCO=1 DCO=2 DCO=3 DCO=4 DCO=5 DCO=6 DCO=7

Basic Clock Module

4-7

MSP430x1xx specifications

The Texas Instruments MSP430x1xx series is a family of ultra-low-power microcontrollers that are highly regarded in the embedded systems community for their versatility and performance. Designed for applications ranging from portable instrumentation to low-power industrial devices, the MSP430x1xx combines flexibility and efficiency with advanced features tailored for energy-sensitive applications.

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In summary, the Texas Instruments MSP430x1xx series of microcontrollers is an excellent choice for developers seeking low-power, high-performance solutions for embedded applications. With an efficient architecture, a rich set of peripherals, and flexible memory options, these microcontrollers are positioned to meet the growing demands of modern electronic designs, particularly in battery-powered and energy-sensitive applications.

Texas Instruments MSP430x1xx Adjusting the DCO frequency, 5. Typical DCOx Range and RSELx Steps

Models: MSP430x1xx