【正文】 is MCS51 microcontroller munication program, on the other hand for the PC, the munication process. In the 9 preparation processes, the development of the two protocols is very important, otherwise it will not guarantee the reliability of data munications, and thus lose the meaning of munication. The munication protocol is agreed as follows: 1) The serial munication baud rate is 1200bps. 2) The frame format is: a start bit, eight data bits, a programmable ninth bit (this bit is sent and received address / data flag), and one stop bit. 3) Set the address of the microcontroller code F1H. Contact before sending the data in the address code, such as the address code is the correct transmission of data, or to contact the address code. 4) no parity. The munication of data accumulation and verification of the method, that is, each carrying one set of data (number of custom, is set to 100), a cumulative and whether the correct checksum, the right to send you back to the 00H, or loopback FFH. 5) munication can interrupt transmission and query. Here are ways to search for in the munication. 6) PCcontact for the initiative to contact MCS 51 microcontroller. 7) PC machine using COM2 munications. VI. CONCLUSION The hardware of serial port munication is designed based on RS232, and the software of munication module between PC microputer and single chip microputer were programmed by using C++ Build and assembly langua ge. The control system runs well on industry field, and controls the stepping motor? Start/Stop and Forward/Reversal rotation by controlling single microputer. The PC microputer sends out control instruction to the single microputer by friendly user interface. 10 REFERENCES [1] Fan Yizhi, Jiang Wenxiang, Chen Liyuan. Serial munication control based C++Build and RS232. Beijng: Tsinguua University Press, 2020, pp. 218 [2] Gou Suai. C++Builder Programmer?s Guide. Beijing: Beijing Hope Electronic Press, 2020, pp. 16 [3] Liu Yanling. The Use of Communication Between MCS51 Single Chip Microputer and PC Microputer with MAX232. Journal of Tianjin Institute of Technology, 1999, Vol, 15(2): pp. 5658 [4] Yang Guoxia. Dealing With The Data Communication Between The Serial Port And The Main Program by Message. Journal of The Hebei Academy of Sciences, 2020, Vol. 18(4): pp. 220223 [5] LI Buyin, Jiang Shenglin, Lu Wenzhong, Zhou Dongxiang. Serial Communication Programming Design Based on C Language. Journal of Transcluction Technology, 2020, Vol. (2), pp. 6566 [6] Wang serial munication of single chip microputer and PC. Modern Electronic Technique, 2020,119, pp. 6870 11 基于 RS232 的串行通信設(shè)計(jì) 摘 要 論文抽象地論述了串行通信的主要原則，提出了在 RS232 的基礎(chǔ)上，設(shè)計(jì)串行通訊硬電路 的方法。 single chip microputer。 10V output voltage level required, so using this chip serial munications interface system as long as a single +5 V power supply can. MAX232 requires four external electrolytic capacitors C1, C2, C3, and C4, is the internal capacitance of a power conversion requirements are 1μF/25V1 should choose its value and should be as close as possible tantalum chip capacitor 1C5 is 0. 1μF decoupling capacitor. MAX232 pin T1IN, T2IN, R1OUT, R2OUT to pick TTL / CMOS level pin 1 pin T1OUT, T2OUT, R1IN, R2IN to access RS 232C level 1 so the pin TTL / CMOS level T1IN, T2IN MCS51 pin should be connected to the serial transmit pin TXD。該步進(jìn)電機(jī)是通過(guò)單芯片來(lái)實(shí)現(xiàn)微機(jī)控制脈沖分配的。 串行通信是最古老的溝通機(jī)制之一。使用串行端口，你可以連接到調(diào)制解調(diào)器，鼠標(biāo)或其它設(shè)備，如一個(gè)橋梁 /路由器進(jìn)行配置。該數(shù)據(jù)位可以是五、六、七或八位，基于商定而定。一個(gè)校驗(yàn)位可以是以下內(nèi)容：奇數(shù)，偶數(shù)，標(biāo)記，空白或無(wú)（空的奇偶位標(biāo)志幾乎總是被使用）。在異步通信中，數(shù)據(jù)是一幀一幀傳送的 ,每一串行幀的數(shù)據(jù)格式由一位起始位 ,5～ 8位的數(shù)據(jù)位 ,一位奇偶校驗(yàn)位 (可省略 )和一位停止位四部分組成。串行通信擁有很多的標(biāo)準(zhǔn)接口，如 RS232， RS485， USB 接口和IEEE1394。該標(biāo)準(zhǔn)適用于 DCE和 DTE間的串行二進(jìn)制通信 ,最高數(shù) 據(jù)傳送速率可達(dá) , 13 最長(zhǎng)傳送電纜可達(dá) 15米。為了實(shí)現(xiàn)可靠的，實(shí)時(shí)的傳輸，該系統(tǒng)采用三線連接方式，即 RS232端口的 GND引腳， RXD 引腳和 TXD 的引腳與外部端口連接，如圖 1所示。 MAX232芯片是 Maxim公司生產(chǎn)的低功耗、單電源雙 RS232發(fā)送 /接收器，適用于各種 EIA232E 和 14 的通信接口。因此，它適應(yīng)了串行通信接口。子程序的串口接收數(shù)據(jù)，逐個(gè)發(fā)送脈沖，通過(guò)上升沿判斷指令子程序和中斷子程序發(fā)送的數(shù)據(jù)。經(jīng)過(guò)單片機(jī)接收數(shù)據(jù)，并調(diào)用串口中斷子程序，它第一次發(fā)送的數(shù)據(jù)被處理。這時(shí)，單片機(jī)返回到主程序和等待接收指令。 子接口很簡(jiǎn)單，其中的子接口的參數(shù)設(shè)置，如波特率通信模塊的芯片已被設(shè)置為2400Bps，在計(jì)算機(jī)上的端口的默認(rèn)設(shè)置 2400Bps。 （ 4）無(wú)奇偶校驗(yàn)位。 PC 微機(jī)通過(guò)友好 的用戶界面向單片機(jī)發(fā)送控制指令。 17 （ 5）通信可以有中斷傳送方式和查詢方式。 串行通信程序包括兩部分 ,一部分是 MCS51單片機(jī)的通信程序 ,另一部分是 PC機(jī)的通信程序。串行口通信可以利用兩種方式：一是注冊(cè)組件，生成的 C++本身并不提供單獨(dú)的串行通訊組件，但是它可通過(guò)已注冊(cè)的 Microsoft MSComm32成分，生成相對(duì)簡(jiǎn)單的 VB， VC 代碼。 16 如果第一個(gè)數(shù)據(jù)是一個(gè)數(shù)字標(biāo)記“ 49”，這意味著步進(jìn)電機(jī)反轉(zhuǎn)，則單片機(jī)接收到發(fā)送來(lái)的速度和步驟信息。由單片機(jī)接收到的數(shù)據(jù)包括一些信息，如速度，步驟和開 /關(guān)指示，由于緩沖區(qū)的大小足夠把這些數(shù)據(jù)發(fā)送到電腦中，所以省略了軟件握手協(xié)議，以提高 CPU 利用率。因此，用它來(lái)作為電壓轉(zhuǎn)換器適用。 10V 電壓 ,所以采用此芯片接口的串行通信系統(tǒng)只要單一的 +5V電源就可以。為了溝通上位機(jī)和下位機(jī)，就需要將單片機(jī)輸出的 TTL 電平進(jìn)行轉(zhuǎn)換。 RS232C標(biāo)準(zhǔn)的電平采用負(fù)邏輯 ,規(guī)定 +3V～ +15V之間的任意電平為邏輯“ 0”電平 ,3V～ 15V 之間的任意電平為邏輯“ 1”電平 ,與 TTL和 CMOS 電平是不同的。 RS485的數(shù)據(jù)傳輸 具有抗噪聲的特點(diǎn)，因此它通常用于工業(yè)生產(chǎn)。 PC 機(jī)采用可編程串行異步通信控制器 8250來(lái)實(shí)現(xiàn)異步串行通信。然而，校驗(yàn)位可用于改善完整數(shù)據(jù)的傳送。數(shù)據(jù)位被 發(fā)送完后，就會(huì)發(fā)送一個(gè)停止位。它的優(yōu)點(diǎn)是只需一對(duì)傳輸線進(jìn)行傳送信息 ,因此其成本低 ,適用于遠(yuǎn)距離通信 。顧名思義，一個(gè)串行端口發(fā)送和接收串行數(shù)據(jù)，一次一位數(shù)據(jù)。上位機(jī)與下位機(jī)之間的通信有兩個(gè)方法，它們分別 是并行通信和串行通信。 R1IN, R2IN should be connected PCsender TD. MAX232 chip has a voltage converter which can transform the voltage of +5 V to the required voltage. Therefore, it adapts to the serial munication inter face, moreove