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EIA-232 Bus // RS-232 bus |
| 作者：iC921 栏目：通信技术 |
定义： TXD: Transmit Data; The data sent from the Data Terminal and received by the Data Set. RXD: Receive Data; The data sent from the Data Set and received by the Data Terminal. DTR: Data Terminal Ready; Used by the Data Terminal to signal to the Data Set that it is ready for operation, active high. DSR: Data Set Ready; Used by the Data Set to signal to the Data Terminal that it is ready for operation and ready to receive data, active high. RTS: Request To Send; Used by the Data Terminal to signal the Data Set that it may begin sending data. The Data Set will not send out data with out this signal, active high. CTS: Clear To Send; Used by the Data Set to signal the Data Terminal that it may begin sending data. The Data Terminal will not send out data with out this signal, active high. CD: Carrier Detect; Used by the Data Set to indicate to the Data Terminal that the Data set has detected a carrier (of another DEVICE). RI: Ring Indicator; Used by the Data Set to indicate to the Data Terminal that a ringing condition has been detected. GND: Ground; The common return for all signals on the interface. When using SOFTWARE Flow CONTROL(XON, XOFF); you ONLY need 3 lines, TX (data), RX (data), and GND. XON being equal to ready, XOFF equal to not ready. ＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝ 连接： EIA-232 Bus Pin-OutThe specification ONLY defines the pin-out for a 25 pin D CONNECTOR; how ever, the 9 pin is used more often (defined by EIA-574). A 26 pin CONNECTOR is also called out. EIA-561 calls out an 8 pin CONNECTOR (RJ-45). RS232C indicates a DB25, RS232D indicates an RJ45. Although this site, in general, calls out DB9 and DB25 style CONNECTORs, the real term for a 9-pin D-sub is DE9. A listing of Dsub CONNECTOR manufacturers is listed on the d-sub CONNECTOR manufacturers {International Organization for Standardization} developed the OSI architectural MODEL. The MODEL is divided in seven layers, with layers 1 to 4 called the lower layers and 5 to 7 the upper layers. Layer Responsibilities: Layer 7. Application Layer: The highest layer. Generates or interprets data, may also provide encryption or decryption. Applications using the network learn how to send a request, how to specify a filename over the net, how to respond to a request. Protocol Data Unit [PDU] is called Data at this layer. This layer interfaces directly to and performs common application services for the application processes; it also issues requests to the Presentation Layer. The common application services provide semantic conversion between associated application processes. Note: Examples of common application services of general interest include the virtual file, virtual terminal, and job transfer and manipulation protocols. Layer 6. Presentation Layer: Determines how computers represent data [ASCII, GIF |
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| 作者： iC921 于 2006/1/30 5:41:00 发布：
Encoding Dictionary, terms, and definitions CMI Encoding Coded Mark Inversion doubles the data rate. A zero is sent as a low to high [01] transition, while a one is sent as either a one [1] or zero [0] depending on the previous state. If the previous state was high the one is sent as a zero [0], if it was low the one is sent as a one [1].  CMI Data Encoding CSMA/CD (Carrier Sense Multiple Access/Collision Detection) A local area network access method in which contention between two or more stations is resolved by collision detection. When two stations transmit at the same time, they both stop and signal a collision has occurred. Each then tries again after waiting a predetermined time period. To avoid another collision, the stations involved each choose a random time interval to schedule the retransmission of the collided frame. To make sure that the collision is recognized, Ethernet requires that a station must continue transmitting until the 50 microsecond period has ended. If the station has less than 64 bytes of data to send, then it must pad the data by adding zeros at the end. Used with for example.  NRZI Encoding Return-To-Bias (RB) Encoding The RB encoding method uses magnetic tape that is pre-set to one of the two polarities (+ or -). This pre-sets the magnetic tape to all zeros. DIGITAL ones are then recorded onto the magnetic tape by magnetizing the tape in the opposite polarity. After each one PULSE, the tape returns to its original bias condition. Return-To-Zero (RZ) Encoding The RZ encoding method sends a '0' level as 0 volts, and sends a '1' level as +volts [for the first half of the bit time] followed by 0 volts [for the second half of the bit time]. So a '0' is twice as LONG as '1', because a '1' is sent as a +v and then a 0v. If the data sequence is all high, then the pattern sent is 1,0,1,0 ... The frequency of the data rate for all an all high pattern defines the bandwidth. Symbol A reformatted character. In the example Symbol format below, each symbol has three 1's and three 0's:
FanOut: Integrated CIRCUIT [IC] Fan-Out is the ability of one DEVICE to drive some NUMBER of other DEVICEs. Fan-Out is easily determined by finding the OUTPUT drive current of the source and the input current requir |
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| 作者： iC921 于 2006/1/30 23:49:00 发布：
电缆CABLE STANDARD RS-232 Low-Noise CABLESThe best CABLE for runs up to 50 feet in low-noise environments.>>注意：这里说明长距离通讯是有条件的！！  FeaturesWith RS-232 you can run a CABLE from a PC to a MODEM up to 50 feet (15.2 m) away. If you’re troubleshooting and need to check a particular LEAD, the CONNECTOR hoods can be opened and CABLEs can be repinned. Order the right NUMBER of conductors for your application: 25-Conductor CABLE — Supports all 25 LEADs on the DB25 CONNECTOR. It’s ideal for any application that uses all LEADs and also for use in IBM® compatible parallel applications. 16-Conductor CABLE — For sync applications where full MODEM CONTROL is required in addition to some secondary tests and secondary MODEM CONTROL LEADs (Pins 1–8, 15, 17, 20–25). 12-Conductor CABLE — Supports all STANDARD MODEM CONTROL LEADs, plus clocking LEADs and ring indicate for sync operation (Pins 1–8, 15, 17, 20, 22). 7-Conductor CABLE — Used in async applications requiring additional MODEM CONTROL LEADs for HARDWARE handshaking and flow CONTROL (Pins 2–4, 6–8, 20). 4-Conductor CABLE — Used ONLY in async applications where flow CONTROL is provided by SOFTWARE (such as X-ON/X-OFF). STANDARD pin arrangements SUPPORT your Transmit and Receive data LEADs, Signal Ground, and Data Terminal Ready (Pins 2, 3, 7, 20). SpecificationsCABLE Construction — PVC Conductor Gauge — 22 AWG (7 x 30) Mutual Capacitance — 50 pF/ft. Resistance — <16 ohms/1000 ft. SHIELD — None Buying TipsNOTE: Specify gender when ordering. NOTE: This CABLE is straight wired. －－－－－－－－－－－ 以下主要是帮助了解规格，仅供参考
25 Conductors (12 1/2 Pairs)—Pins 1–25
25 Conductors (12 1/2 Pairs)—Pins 1–25
25 Conductors (12 1/2 Pairs)—Pins 1–25
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