Datasheet

www.ti.com

Basic Clock Module+ Introduction

5.1 Basic Clock Module+ Introduction

The basic clock module+ supports low system cost and ultralow power consumption. Using three internal

clock signals, the user can select the best balance of performance and low power consumption. The basic

clock module+ can be configured to operate without any external components, with one external resistor,

with one or two external crystals, or with resonators, under full software control.

The basic clock module+ includes two, three or four clock sources:

• LFXT1CLK: Low-frequency/high-frequency oscillator that can be used with low-frequency watch

crystals or external clock sources of 32768 Hz or with standard crystals, resonators, or external clock

sources in the 400-kHz to 16-MHz range.

• XT2CLK: Optional high-frequency oscillator that can be used with standard crystals, resonators, or

external clock sources in the 400-kHz to 16-MHz range.

• DCOCLK: Internal digitally controlled oscillator (DCO).

• VLOCLK: Internal very low power, low frequency oscillator with 12-kHz typical frequency.

Three clock signals are available from the basic clock module+:

• ACLK: Auxiliary clock. ACLK is software selectable as LFXT1CLK or VLOCLK. ACLK is divided by 1,

2, 4, or 8. ACLK is software selectable for individual peripheral modules.

• MCLK: Master clock. MCLK is software selectable as LFXT1CLK, VLOCLK, XT2CLK (if available on-

chip), or DCOCLK. MCLK is divided by 1, 2, 4, or 8. MCLK is used by the CPU and system.

• SMCLK: Sub-main clock. SMCLK is software selectable as LFXT1CLK, VLOCLK, XT2CLK (if available

on-chip), or DCOCLK. SMCLK is divided by 1, 2, 4, or 8. SMCLK is software selectable for individual

peripheral modules.

The block diagram of the basic clock module+ in the MSP430F2xx devices is shown in Figure 5-1.

The block diagram of the basic clock module+ in the MSP430AFE2xx devices is shown in Figure 5-2.

273

SLAU144J–December 2004–Revised July 2013 Basic Clock Module+

Submit Documentation Feedback