F28035 SCI 学习笔记.doc

SCI CommunicationLSPCLK = SYSCLK/4(default) Low Speed Prescaler异步通讯：发送端可以在任意时刻开始发送字符，因此必须在每一个字符的开始和结束的地方加上标志，即加上开始位和停止位，以便使接收端能正确地将每一个字符接收下来。异步通信的好处是通信设备简单、便宜，但传输效率较低（因为开始位和停止位的开销所占比例较大）。一般通讯格式： One start bit One to eight data bits An even/odd parity bit or no parity bit One or two stop bits同步异步最大得区别应该在于：同步中传输方和接受方使用同步时钟（即波特率是一样的，时序是一样的），而异步通讯允许双方使用各自不同的时钟。同步通信可用于点对多点；异步通信只适用于点对点。 full-duplex operation 全双工SCI Communication Format（原理性）8个SCICLK确定一个信号位，起始位4次采样确定，数据位三次采样为准确定中断SCI Port Interrupts 包括接收中断和发送中断1接收/break中断 当RX/BK INT ENA = 1 ，A. RXRDY=1接收完毕，等待读取；读取SCIRXBUF register后RXRDY自动清零； B. A break detect condition occurs (the SCIRXD is low for ten bit periods following a missing stop bit).BRKDT=1;2 接收错误中断 当RX ERR INT ENA =1 时SCI receiver error 接收错误。RX ERROR interrupt flag which is a logical OR 逻辑或of the FE, OE, BRKDT, and PE conditions.3 发送中断 当TX INT ENA=1 ，TXRDY=1表示发送给了TXSHF完毕，可以对TXBUF写下一个数据，TXRDY=0表示TXBUF里有数据还没发送；优先级： This is indicated by the priority bits which are output from the peripheral to the PIE controller. When both RX and TX interrupt requests are made at the same priority level, the receiver always has higher priority than the transmitter, reducing the possibility of receiver overrun.SCI FIFO 发送和接收分别有4个FIFO存储器ResetStandard SCIFIFO enableInterrupts 2个中断one for transmit FIFO, TXINT and one for receive FIFO, RXINT. RXINT is the common interrupt for SCI FIFO receive, receive error, and receive FIFO overflow conditions. The TXINT of the standard SCI will be disabled and this interrupt will service as SCI transmit FIFO interrupt.Delay Transfer 由SCIFFCT register控制，基本不用。FIFO status bits ；TXFIFO Reset和RXFIFO Reset 使FIFO pointer清零，初始化最后在使能FIFO operation Programmable interrupt levels ;当TXFFST = TXFFIL时产生发送中断，默认：0x00000 for transmit FIFO；当RXFFST = RXFFIL时产生接收中断，默认：0x11111 for receive FIFO 接收Receive FIFO溢出，超过16个字时会发生。More than 16 words have been received in to the FIFO, and the first received word is lost Receive FIFO overflow. This will function as flag, but cannot generate interrupt by itself. This condition will occur while receive interrupt is active. Receive interrupts should service this flag condition.SCI Multiprocessor Communication（多机通讯）原则是There can be only one talker on a serial line at a time. 两种多机通讯方式：Idle-line mode（默认）和Address-bit mode 。其中Address-bit mode的数据中包含一位地址位，表明该字节是否是“地址信息”，地址匹配了才接受后面的数据。编程中：SciaRegs.SCIHBAUD =0x0000;SciaRegs.SCILBAUD =14; /0XC2-9600 ; 0X 97- 19200 ;0x30-38400; 0X 14-128000SCI 配置完之后，需要通过相关恢复如下：SciaRegs.SCICTL1.bit.SWRESET = 1;/ Relinquish