Technology Training that Works Hands of Data Communications, Networking & TCP/IP Troubleshooting

Technology Training that Works Topics  Basics of serial communication  RS-232  RS-422  RS-485

Technology Training that Works Serial Communication  Data is sent and received one bit at a time over a communication channel.  Serial ports  9 pin and 25 pin  Used to communicate with terminals and peripheral devices  Also known as COM port, controlled by UART

Technology Training that Works Parallel Communication  8 (or 16 or 32) bits are sent and received simultaneously  Sent over a bus comprising 8 (or 16 or 32) channels, one for each bit.  Usually used within a device.

Technology Training that Works Connector – Types Types of serial port connectors

Technology Training that Works DTE vs. DCE  Devices that use serial cables for their communication  DTE  Data Terminal Equipment  E.g. computers, printers  Transmits on Pin 2  DCE  Data Communications Equipment  E.g. modems  Transmits on Pin 3

Technology Training that Works Asynchronous vs. Synchronous Asynchronous  No clock sent  Level sync  Character transfer  Susceptible to noise  Slow  Short lengths Synchronous  Clock sent  Edge sync  Packet transfer  Resistant to noise  Fast  Long distances

Technology Training that Works Serial Communication – Keywords  Handshaking - a procedure used to check the link between DTE & DCE before transmitting data  Baud Rate  Transmission speed  Number of bits that are actually being sent over the serial link  Type of Cables  Modem Cable  Null Modem Cables

Technology Training that Works Modem Cable Signal Description 9-pin DTE 25-pin DCE Remarks Carrier Detect (CD)18From Modem Receive Data (RD)23From Modem Transmit Data (TD)32From Terminal/Computer Data Terminal Ready (DTR)420From Terminal/Computer Signal Ground (SG)57From Modem Data Set Ready (DSR)66From Modem Request to Send (RTS)74From Terminal/Computer Clear to Send (CTS)85From Modem Ring Indicator (RI)922From Modem RS-232 Pinouts DB9 to DB25

Technology Training that Works Null Modem Cables Connecting 25 pin to 25 pin for Null Modem Signal description25-pin Signal description Receive Data32Transmit Data 23Receive Data Data Terminal Ready206+8 Data Set Ready + Carrier Detect System Ground77 Data Set Ready + Carrier Detect 6+820Data Terminal Ready Request to Send45Clear to Send 54Request to Send

Technology Training that Works Null Modem Cables Connecting 9 pin to 9 pin for Null modem Signal description9-pin Signal description Receive Data23Transmit Data 32Receive Data Data Terminal Ready46+1 Data Set Ready + Carrier Detect System Ground55 Data Set Ready + Carrier Detect 6+14Data Terminal Ready Request to Send78Clear to Send 87Request to Send

Technology Training that Works RS-232 Standard  Specifies the method of connection of a DTE and a DCE.  A DCE receives data from the DTE and retransmits it to another DCE via a data communications channel such as a telephone link.

Technology Training that Works RS-232 Connections Connection between DTE and DCE using DB-25 connectors

Technology Training that Works Voltage Levels

Technology Training that Works RS-232 Transmitters & Receivers

Technology Training that Works Half Duplex Operational Sequence of RS 232

Technology Training that Works RS-422 Interface Standard  Defines a balanced, or differential, data communications interface  Uses two separate wires for each signal  Permits very high data rates  Minimizes problems with varying ground potentials

Technology Training that Works The EIA-422 Balanced Line Driver Connections

Technology Training that Works EIA 422 Voltages vs. Real Life  EIA voltages: ±6 volts to ±2 volts  In real systems the voltage is between ±5 volts and ±.2 volts  Often the same chips that are used for 485 systems are used for 422  Typical measured voltage is approximately ±2 volts

Technology Training that Works EIA vs. Real Life Simplex  10Mbps  Differential  10 devices Half or full duplex  No speed defined  Differential  Point to point

Technology Training that Works RS-485 Interface Standard  Most versatile EIA standard  Distances of up to 1200m  Data rates of up to 10Mbps  32 line drivers  32 line receivers

Technology Training that Works RS-485  RS-485 is the most common voltage standard in use today for multi-drop communication systems.  This is because …  It is very resistant to noise  It can send data at high speeds  And can go long distances

Technology Training that Works Two-Wire Multidrop

Technology Training that Works Four Wire Network

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