Datasheet

USI Introduction

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14.1 USI Introduction

The USI module provides the basic functionality to support synchronous serial communication. In its

simplest form, it is an 8- or 16-bit shift register that can be used to output data streams, or when combined

with minimal software, can implement serial communication. In addition, the USI includes built-in hardware

functionality to ease the implementation of SPI and I

C communication. The USI module also includes

interrupts to further reduce the necessary software overhead for serial communication and to maintain the

ultra-low-power capabilities of the MSP430.

The USI module features include:

• Three-wire SPI mode support

• I

C mode support

• Variable data length

• Slave operation in LPM4; no internal clock required

• Selectable MSB or LSB data order

• START and STOP detection for I

C mode with automatic SCL control

• Arbitration lost detection in master mode

• Programmable clock generation

• Selectable clock polarity and phase control

Figure 14-1 shows the USI module in SPI mode. Figure 14-2 shows the USI module in I

C mode.

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Universal Serial Interface (USI) SLAU144J–December 2004–Revised July 2013

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