串行通信的传输方式：
单工，半双工，全双工。
51单片机的串口属于全双工通信
异步通信：使用各自的时钟
同步通信：使用相同的时钟
采用8N1模式（8个数据位，n0个校验位，一个停止位，一个起始位，其中起始位是通信标准，必须要有）
使用串口定时器1不能被使用
其中俩个SBUF的名字相同，地址不同，物理上是独立的。
波特率 = (2^SMOD * fosc)/(32 * 12*(256-x))
SMOD默认为0
写串口的工作
1.设置串口工作方式
2.打开ENA
3.设置发送 接收波特率
1）设置定时器1工作方式为8位自动重装方式，即方式2
2）填初值（TH1）
3）打开定时器
<code class="hljs cpp has-numbering" style="display: block; padding: 0px; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-radius: 0px; word-wrap: normal; background: transparent;"><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include <reg52.h></span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">#include "./delay/delay.h"</span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// #include <stdio.h></span><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//初始化</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> uart_init(){ SCON = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0x50</span>; TMOD |= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0x20</span>; TH1 = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0xfd</span>; TR1 = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>;}<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//发送字节</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> uart_send_byte(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">unsigned</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> byte){ SBUF = byte; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(!TI); TI = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>;}<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//发送字符串</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> uart_send_string(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">unsigned</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> *s){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(*s != <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">'\0'</span>) { uart_send_byte(*s); s++; }}<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">//调用主函数</span><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">void</span> main(){ <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">unsigned</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> s[<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>]; <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">unsigned</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">char</span> i = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; uart_init(); uart_send_string(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"please input the char:\n"</span>); <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span>(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">1</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(RI) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(i >= <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">10</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">if</span>(SBUF == <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">' '</span>) { <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">break</span>; } s[i] = SBUF; i++; RI = <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; } delay_ms(<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">5</span>); } uart_send_string(s); uart_send_string(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"\t\n"</span>);}</code> 0 0
