【正文】 應中斷和相關(guān)數(shù)據(jù)發(fā)送到 RAM 存儲 ,然后“ 0”寫入 ,低水平在 555 年 銷觸發(fā)計時器 ,555 定時器的輸出脈沖取決于 R、 C 和 VCC。正確的信息返回時 ,主機通過 P2 驅(qū)動相應的 LED 指示器顯示端口 ,表明已經(jīng)成功發(fā)送的請求信號。 擴展包括單片機 AT89C52,電力線調(diào)制芯片 PL2102 和一些外圍電路。相反，它會增加發(fā)射電流和波形失真。它將通過 PL2102 的 PSK 輸出端口輸出的載波調(diào)制信號的功率。 C2， C3 和 L2 組成并聯(lián)諧振電路的諧振頻率為 120 千赫。 電力線載波電路主要包括電力線耦合電路，信號接收電路、信號發(fā)射電路，它的發(fā)送和接收的電力線載波信號。 AT89C52 40 針 ,32 外部雙向輸入 /輸出 (I / O)端口 ,包括兩個外部中斷端口、三個 16 位可編程定時計數(shù)器 ,兩個全雙工串行通信端口 ,兩個寫端口線。具有抗干擾一優(yōu)越的性能和抗衰落性能與國內(nèi)外同類產(chǎn)品的性價比，等等。除了具有基本的通信控制功能，智能家電還建立了五種常用的功能電路：數(shù)字頻率校正實時時鐘電路， 32 字節(jié)的 SRAM，電壓 監(jiān)控，看門狗定時器復位電路。 III. 系統(tǒng)硬件設(shè)計 電力線載波通信是指利用專用調(diào)制解調(diào)器芯片數(shù)據(jù)調(diào)制和被加載到 50Hz 電源線頻率的發(fā)送過程，然后接收，解調(diào)，恢復數(shù)據(jù)。通信數(shù)據(jù)包由 8 字節(jié)的數(shù)據(jù)，第一和第二個字節(jié)是主機號，第三字節(jié)的命令，第四和第五字節(jié)的擴展地址，第六到第八字節(jié)數(shù)據(jù)。 II. 系統(tǒng)結(jié)構(gòu)及工作原理 呼叫系統(tǒng)主要由主機，分機及電源線載波電路，主機安裝在病房的護士值班室，擴展被安裝在病房，宿主可以控制多個擴展名，一 220V 民用電源線作為傳輸信道，以實現(xiàn)兩個主機和分機之間溝通方式。因此，它已成為可能，利用低壓電力線作為傳輸介質(zhì)，利用擴頻，數(shù)字編碼，單片機控制技術(shù)實現(xiàn)病房呼叫。 隨著通信技術(shù)的發(fā)展，人們對電力線通信技術(shù)，卡麗做了大量的研究工作。它是提高醫(yī)院的護理水平的必備設(shè)備之一。中文 3100 字 外文資料原文 Design Of Medical Ward Call System Based On Power Line Carrier Technology I. INTRODUCTION The medical ward call system is a kind of call tools when the patient needs access to care or diagnosis, patient39。s PSK OUT port. It is added to the coupling coil after filtering integer by C1 and L1, and is fed into the power line through the coupling coil. The carrier modulation signal outputted by PL2102 is amplified through the power amplifier circuit, filter out signal noise and false signal. Capacitor C1, inductor L1 (18uH/200mA) of the integral filter circuit are used to adjust the emission current and waveform, reducing C1 and increasing L1 will reduce the emission current and improve the waveform. Conversely, it will increase the emission current and waveform distortion. As the coil load capacity is a fixed value, adjusting C1 and L1 will affect the transmission power and their power of the coil. Meanwhile, the emission voltage VHH affects size of the transmitted power, following the launch voltage drop, transmit power has declined, the higher the voltage is, the greater the transistors own power consumption is. This emission voltage is typically chosen between lOV 一18V [6]. of the extension circuit The extension includes MCU AT89C52, power line modulation chip PL2102 and some peripheral circuits. Schematic is shown in Fig. 3. Eight request button switches are connected to the port PO of the MCU AT89C52, when a button is pressed, the input state of the port PO corresponding to this button is 0. When the MCU confirms that the host calls its address, it will scan 8bit I /O port status of port P0, once a key is pressed, the request information corresponding to this button will immediately send to the host, and wait for the host to confirm. When the correct information is returned, the host drives the corresponding LED indicators display via P2 port to indicate that a request signal sent successfully. Eight button switches for request are numbered, each switch represents a kind of information for request, which can be defined by users [7]. and RESET port of the MCU AT89C52 connect the backup power and powerdown protection circuit in order to ensure that the system can work properly when power failure occurs. If the system has detected an imminent loss of power signal,