Chapter 6 Transmission of Digital Data Interfaces and Modems Digital Data Transmission DTE-DCE Interface Other Interface Standards Modems WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Figure 6-1 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Parallel Transmission Figure 6-2 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Serial Transmission Figure 6-3 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998 Advantage: reduces the cost of transmission over parallel by roughly a factor of n.

Asynchronous Transmission Figure 6-4 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Synchronous Transmission Figure 6-5 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Asynchronous at byte level, but the bits are still synchronized; Asynchronous We send bits one after the another without start/stop bits. It is the responsibility of the receiver to group the bits. Synchronous

In asynchronous transmission, the gap time between bytes is a) fixed b) Variable c) A function of the data rate d) Zero

DTEs and DCEs Figure 6-6 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

DTE-DCE interface Figure 6-7 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

DTE-DCE Interface(cont’d) DTE(Data Terminal Equipment) ~ is any device that is a source of destination for binary digital data  terminal  microcomputer  computer  printer  fax machine and so on

DTE-DCE Interface(cont’d) DCE(Data Circuit-Terminating Equipment) ~ is any device that transmits or receives data in the form of an analog or digital signal through a network  Modulator/demodulator

A _____ is a device that is a source of or destination for binary digital data a) Data terminal equipment b) Data transmission equipment c) Digital terminal encoder d) Digital transmission equipment

The EIA (Electronics Industries Association) and the International Telecommunication Union-Telecommunication Standards Committee (ITU-T) have been involved in developing DTE-DCE interface standards. EIA standards are called EIA – 232 EIA – 442 EIA – 449 and so on. ITU – T standards are called the V series and the X series.

15 DTE-DCE Interface(cont’d) sending the data ~ To be recognized as data, the amplitude of a signal must fall between 3 and 15 volts or between –3 and –15 volts

Control Figure 6-9 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

EIA-232 Figure 6-10 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Data Pins Figure 6-10-continued WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Control Pins Figure 6-10-continued WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Timing Pins Figure 6-10-continued WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Other Pins Figure 6-10-continued WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998

Figure 6-11 WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998 Synchronous Full-Duplex Transmission

Figure 6-11-continued WCB/McGraw-Hill  The McGraw-Hill Companies, Inc., 1998 Synchronous Full-Duplex Transmission

EIA 449 INTERFACE STANDARD

EIA The RS-449 specification, also known as EIA- 449 or TIA-449, defines the functional and mechanical characteristics of the interface between data terminal equipment and data communications equipment. The electrical signaling standards intended for use with RS-449 are RS-422 for balanced signals, and RS-423 for the unbalanced signals, with data rates to 2 Mbits/s. Though never applied on personal computers, this interface is found on some network communication equipment. The full title of the standard is EIA-449 General Purpose 37-Position and 9-Position Interface for Data Terminal Equipment and Data Circuit-Terminating Equipment Employing Serial Binary Data Interchange.