Lecture Microcomputer principles and applications - Chapter 9: Serial communication interface

11:56:01<br /> <br /> Chapter 9<br /> Serial communication interface<br /> <br /> 11:56:01<br /> <br /> 9.1 USCI Overview<br /> The universal serial communication interface (USCI) modules<br /> support multiple serial communication modes. Different USCI<br /> modules support different modes.<br /> The USCI_Ax modules support:<br /> •<br /> •<br /> •<br /> •<br /> <br /> UART mode.<br /> Pulse shaping for Infrared Data Association (IrDA)<br /> communications.<br /> Automatic baud rate detection for Local Interconnect Network<br /> (LIN) communications.<br /> Serial Peripheral Interface (SPI) mode.<br /> <br /> The USCI_Bx modules support:<br /> •<br /> •<br /> <br /> Inter-Integrated Circuit (I2C or I2 C) mode.<br /> SPI mode.<br /> Microcomputer principles and applications<br /> <br /> 11:56:01<br /> <br /> 9.2 UART Mode<br /> UART = Universal asynchronous receiver/transmitter.<br /> UART mode (UCSYNC bit=0) features include:<br /> •<br /> •<br /> •<br /> •<br /> •<br /> •<br /> •<br /> •<br /> •<br /> •<br /> <br /> 7- or 8-bit data with odd, even, or non-parity.<br /> Independent transmit and receive shift registers.<br /> Separate transmit and receive buffer registers.<br /> LSB-first or MSB-first data transmit and receive.<br /> Built-in idle-line and address-bit communication protocols for<br /> multiprocessor systems.<br /> Receiver start-edge detection for auto-wake up from LPMx<br /> modes.<br /> Programmable baud rate with modulation for fractional baud<br /> rate support.<br /> Status flags for error detection and suppression.<br /> Status flags for address detection.<br /> Independent interrupt capability for receive and transmit.<br /> Microcomputer principles and applications<br /> <br /> 11:56:01<br /> <br /> 9.3 UART Mode<br /> •<br /> <br /> •<br /> •<br /> <br /> •<br /> <br /> Start - Part of the serial interface’s job is to frame the bits of<br /> each data, using a start bit to indicate the start of the data. The<br /> start bit then serves to synchronize the sender and the receiver.<br /> Stop - Part of the serial interface’s job is to frame the bits of<br /> each data, using a stop bit for the end of the data.<br /> Baud rate - The start bit marks the beginning of the sender’s<br /> data. From the start bit the receiver can count clock ticks to<br /> determine when to read each data bit. The baud rate defines the<br /> time each bit exists or the time to wait between reading (or<br /> sending) each bit.<br /> A parity bit (or check bit) - a bit added to the end of a string of<br /> binary code that indicates whether the number of bits in the<br /> string with the value one is even or odd. Parity bits are used as<br /> the simplest form of error detecting code.<br /> <br /> Microcomputer principles and applications<br /> <br /> 11:56:01<br /> <br /> 9.3 UART Mode<br /> A start bit (0), 8 bits of data (least significant bit first), and a stop bit<br /> (1). This protocol is used for both transmitting and receiving.<br /> One frame<br /> 5V<br /> <br /> b<br /> <br /> b3<br /> <br /> b<br /> <br /> b5<br /> <br /> b<br /> §<br /> <br /> b1<br /> <br /> ¦<br /> <br /> b<br /> <br /> ¥<br /> <br /> Start<br /> <br /> ¤<br /> <br /> Serial port<br /> <br /> b7<br /> <br /> Stop<br /> 0V<br /> <br /> Microcomputer principles and applications<br /> <br />