Datasheet

USCI Overview www.ti.com
16.1 USCI Overview
The universal serial communication interface (USCI) modules support multiple serial communication
modes. Different USCI modules support different modes. Each different USCI module is named with a
different letter (for example, USCI_A is different from USCI_B). If more than one identical USCI module is
implemented on one device, those modules are named with incrementing numbers. For example, if one
device has two USCI_A modules, they are named USCI_A0 and USCI_A1. See the device-specific data
sheet to determine which USCI modules, if any, are implemented on each device.
The USCI_Ax modules support:
• UART mode
• Pulse shaping for IrDA communications
• Automatic baud rate detection for LIN communications
• SPI mode
The USCI_Bx modules support:
• I
2
C mode
• SPI mode
16.2 USCI Introduction: SPI Mode
In synchronous mode, the USCI connects the MSP430 to an external system via three or four pins:
UCxSIMO, UCxSOMI, UCxCLK, and UCxSTE. SPI mode is selected when the UCSYNC bit is set and SPI
mode (3-pin or 4-pin) is selected with the UCMODEx bits.
SPI mode features include:
• 7- or 8-bit data length
• LSB-first or MSB-first data transmit and receive
• 3-pin and 4-pin SPI operation
• Master or slave modes
• Independent transmit and receive shift registers
• Separate transmit and receive buffer registers
• Continuous transmit and receive operation
• Selectable clock polarity and phase control
• Programmable clock frequency in master mode
• Independent interrupt capability for receive and transmit
• Slave operation in LPM4
Figure 16-1 shows the USCI when configured for SPI mode.
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Universal Serial Communication Interface, SPI Mode SLAU144J–December 2004–Revised July 2013
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