基于c54xdsp的基帶調制解調器的設計-資料下載頁

　　

【正文】 regular intervals are equipped with relay amplification equipment to ensure clear voice. 在這些設備上若再配置Modem，則能通電話的地方就可傳輸數據。 Configure these devices Ruozai Modem, is to place the phone can transmit data. 一般電話線路的話音帶寬在300～3400Hz 范圍，用它傳送數字信號，其信號頻率也必須在該范圍。 Ordinary telephone lines in the 300 ~ 3400Hz voice bandwidth, range, use it to transmit digital signals, the signal must also be in the range of frequencies. 常用的調制方法有三種:頻移鍵控(FSK)、相移鍵控(PSK) 、相位幅度調制(PAM)。 There are three monly used methods of modulation: frequency shift keying (FSK), phase shift keying (PSK), phaseamplitude modulation (PAM). Modem通常有三種工作方式:掛機方式、通話方式、聯機方式。 Usually there are three ways of working Modem: hang up mode, call mode, online. 電話線未接通是掛機方式；雙方通過電話進行通話是通話方式；Modem已聯通，進行數據傳輸是聯機方式。 Telephone line is not connected to hook mode。 both the phone call is a call mode。 Modem had interchange, data transmission is online. 數模轉換的調制方法有三種： Digitalanalog conversion of the modulation in three ways: (1)頻移鍵控(FS K) ：用特殊的音頻范圍來區別發送數據和接收數據。 (1) frequency shift keying (FSK): with a special scope to distinguish between audio send data and receive data. 如調頻ModemBell103型發送和接收數據的二進制邏輯被指定的專用頻率是:發送，信號邏輯0、頻率1070Hz，信號邏輯頻率1270Hz；接收，信號邏輯0、頻率20 25Hz，信號邏輯頻率2225Hz。 FM ModemBell103 type, such as sending and receiving binary data is designated a special frequency of the logic is: to send the signal logic 0, the frequency of 1070Hz, signal logic 1, the frequency 1270Hz。 receiver, the signal logic 0, Frequency 20 25Hz, the signal logic 1, frequency of 2225Hz. (2)相移鍵控(PSK) ：高速的Modem常用四相制，八相制，而四相制是用四個不同的相位表示00、011四個二進制數，如調相ModemBell212A型。 (2) phase shift keying (PSK): highspeed Modem mon fourphase system, eightphase system, while the fourphase system is expressed in four different phases of four binary numbers 00,01,10,11, such as PM ModemBell212A type. 該技術可以使3 00bps的Modem傳送600bps的信息，因此在不提高線路調制速率僅提高信號傳輸速率時很有意義，但控制復雜，成本較高，八相制更復雜。 The technology allows 3 00bps to 600bps Modem transmission of information, and therefore not only improve the line to improve the signal modulation rate when the transmission rate makes sense, but the control plexity, high cost, eightphase system more plex. (3)相位幅度調制(PAM) ：為了盡量提高傳輸速率，不提高調制速率，采用相位調制和幅度調制結合的方法。 (3) phaseamplitude modulation (PAM): In order to maximize the transmission rate, modulation rate does not increase, the phase modulation and amplitude modulation using the method of bining. 它可用16個不同的相位和幅度電平，使1200bps的Modem傳送19200bps的數據信號。 It can be 16 different phase and amplitude level, so that the Modem 1200bps 19200bps data transmission signal. 該種Modem一般用于高速同步通信中。 The kind of Modem for highspeed synchronous munications generally. 調制解調器通電后，通常先進入掛機方式，通過電話撥號撥通線路后進入通話方式，最后通過Modem的“握手”過程進入聯機方式。 Modem is powered, usually the first way into the hook, dial the telephone dialup lines and entered the call, and finally through the Modem39。s handshake process into the online. 正常使用時，由使用者通過控制電話機或Modem前面板的按鍵、內部開關實現三種方式間的轉換。 Normal use, by the user through the phone or Modem front panel control buttons, an internal switch between three ways to achieve the conversion. 調制解調器與計算機連接是數據電路通信設備DCE（DataCircutterminatingEquipment）與數據終端設備DTE(DataTerminalEquipment)之間的接口問題。 Modem and puter to connect the data circuit munications equipment DCE and data terminal equipment DTE the interface between. DCE與DTE之間的接口是計算機網絡使用上的一個重要問題。 DCE and DTE interface between the use of puter networks is an important issue. 任何一個通信站總要包括DCE與DTE，因此確定一個統一的標準接口，特別是對公用數據網有重要的意義。 Any munication stations always have to include DCE and DTE, therefore to establish a unified standard interface, especially for public data networks are important. 數據終端設備DTE是產生數字信號的數據源或接收數字信號的數據宿，或者是兩者的結合，像計算機終端、打印機、傳真機等就是DTE。 DTE data terminal equipment is to produce digital data signal source or receiving digital signal data places, or a bination of both, like puter terminals, printers, fax machines, etc. is DTE. 將數據終端設備DTE與模擬信道連接起來的設備就叫數據電路通信設備DCE，像Modem就是DCE。 DTE data terminal equipment connected with the analog channels called data circuit equipment munications equipment DCE, as the Modem is DCE. DTE與DCE之間的連接標準有CC IT ，與EIARS423A兼容，是一種半平衡電氣特性接口 The connection between the DTE and DCE standards CC IT , and EIARS423A patible, is a semibalanced electrical characteristics of interfaces 普通的Modem通常都是通過RS232C串行口信號線與計算機連接。 Usually through the ordinary Modem RS232C serial port signal lines and puter connections. RS232是一種歷史悠久的計算機接口標準。 RS232 is a long history of puter interface standards. （RS本是RemendStandard的縮寫），它于1969年被國際組織認可。 (RS RemendStandard this is the abbreviation), which in 1969 recognized by the international organization. RS232的定義包括電氣特性(如電壓值)、機械特性(如接頭形狀)及功能特性(如腳位信號)等。 RS232 is defined to include electrical features (such as voltage value), mechanical properties (such as joint shape) and functional characteristics (such as the pin signal) and so on. 它允許一個發送設備連接到一個接收設備以傳送資料；其原始規范的最大傳輸速度為20Kbps，但事實上，現在的應用早已遠超過這個速度范圍。 It allows a sending device to a receiving device to send information。 its original specification maximum transmission speed of 20Kbps, but in fact, the present application has already far exceeded the speed range. RS23 2可說是相當簡單的一種通信標準，若不使用硬件流控，則最少只需利用三根信號線，便可做到全雙工的傳輸作業。 RS23 2 can be a very simple munication standard, if not using hardware flow control, then at least only use three signal lines, can be fullduplex transmission operation. RS232的電氣特性是屬于非平衡傳輸方式，抗干擾能力較弱，故傳輸距離較短，約為15米左右而已。 The electrical characteristics of RS232 is a nonbalanced transmission, antijamming capability is weak, so the transmission distance is shorter, about 15 meters only. RS232C串行口信號分為三類：傳送信號、聯絡信號和地線。 RS232C serial port signal is divided into three categories: transmission signal, the signal and ground contact. (1)傳送信號：指TXD(發送數據信號線)和RXD(接收數據信號線)。 (1) send a signal: that TXD (transmit data signal line) and RXD (receive data signal lines). 經由TXD傳送和RXD接收的信息格式為：一個傳送單位(字節)由起始位、數據位、奇偶校驗位和停止位組成。 TXD RXD via transmi