Peripherals; Oscillator And System Clock; Brownout; Digital I/O - Texas Instruments MSP430G2744DA Manual

MSP430G2744, MSP430G2544, MSP430G2444
SLAS892C – MARCH 2013 – REVISED SEPTEMBER 2014
6.9

Peripherals

Peripherals are connected to the CPU through data, address, and control buses and can be handled using
all instructions. For complete module descriptions, see the MSP430x2xx Family User's Guide (SLAU144).

6.10 Oscillator and System Clock

The clock system is supported by the basic clock module that includes support for a 32768-Hz watch
crystal oscillator, an internal very-low-power low-frequency oscillator, an internal digitally-controlled
oscillator (DCO), and a high-frequency crystal oscillator. The basic clock module is designed to meet the
requirements of both low system cost and low power consumption. The internal DCO provides a fast turn-
on clock source and stabilizes in less than 1 µs. The basic clock module provides the following clock
signals:
• Auxiliary clock (ACLK), sourced from a 32768-Hz watch crystal, a high-frequency crystal, or the
internal very-low-power LF oscillator.
• Main clock (MCLK), the system clock used by the CPU.
• Sub-Main clock (SMCLK), the sub-system clock used by the peripheral modules.
(Provided From Factory in Flash Information Memory Segment A)
DCO FREQUENCY
1 MHz
8 MHz
12 MHz
16 MHz

6.11 Brownout

The brownout circuit is implemented to provide the proper internal reset signal to the device during power
on and power off.

6.12 Digital I/O

There are four 8-bit I/O ports implemented—ports P1, P2, P3, and P4:
• All individual I/O bits are independently programmable.
• Any combination of input, output, and interrupt condition is possible.
• Edge-selectable interrupt input capability for all eight bits of port P1 and P2.
• Read and write access to port-control registers is supported by all instructions.
• Each I/O has an individually programmable pullup or pulldown resistor.

6.13 Watchdog Timer (WDT+)

The primary function of the WDT+ module is to perform a controlled system restart after a software
problem occurs. If the selected time interval expires, a system reset is generated. If the watchdog function
is not needed in an application, the module can be disabled or configured as an interval timer and can
generate interrupts at selected time intervals.
44 Detailed Description
Table 6-10. DCO Calibration Data
CALIBRATION REGISTER
CALBC1_1MHZ
CALDCO_1MHZ
CALBC1_8MHZ
CALDCO_8MHZ
CALBC1_12MHZ
CALDCO_12MHZ
CALBC1_16MHZ
CALDCO_16MHZ
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