The RS232 Serial Interfacing

The RS232 Serial Interfacing - MFET 374, Manufacturing...

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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 1 MFET 374 Manufacturing Integration I The RS The RS-232 232 Serial Interface Spring ‘2010 T.E. Kostek The RS-232 Serial Interface • Topics: – Introduction to the RS-232 interfac Introduction to the RS 232 interface – RS-232 specifications – RS-232 terminology – RS-232 data & ground signals – RS-232 handshaking 2 – Typical RS-232 connections – RS-232 diagnostic tools
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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 2 Introduction to the RS-232 Interface • RS-232 is an EIA standard serial interface –EIA -E lectronic I ndustries A ssociation – RS - R ecommended S tandard • The RS-232 standard specifies the electrical, mechanical, and functional details of how two devices communicate over a serial link 3 • RS-232 does not specify protocol, it does not concern itself with bit meaning. Introduction to the RS-232 Interface • The original RS-232 standard was developed in the early 1960’s! • The standard was developed to support serial communications between terminals, modems (mo dulator-dem odulators), and mainframe computers. 4
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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 3 RS-232 Specifications • Data lines –A logic 1 is represented as a voltage between -5 and 25 volts d -25 volts dc logic 0 is represented as a voltage between +5 and +25 volts dc – There is a ±2 volt noise margin: 5 • TX generates at least +5 v. The RX recognizes voltages as low as +3 volts as a logic 0 • TX generates at least -5 v. The RX recognizes voltages as low as -3 volts as a logic 1 RS-232 Specifications • Handshaking lines – Handshaking is necessary when the RX cannot process data as fast as the TX is transmitting – Voltage levels: • +5v to +25v implies that the RX is ready • -5v to -25v implies that the RX is NOT ready – Handshaking lines are inputs to the TX: 6 TX RX Data Handshake
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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 4 RS-232 Specifications • Data rate and distance – Maximum recommended data rate = 20k bps – Maximum recommended cable length = 50 feet • Can use longer cables when employing special low capacitance cable. 2500 pf 50 pf/f = 50 ft 7 50 pf/ft Maximum capacitance allowed on the cable Typical RS-232 cables have 50 pf/ft of capacitance RS-232 Terminology • Recall that RS-232 was developed to support serial communications between terminals, modems, and mainframe computers. Terminal MODEM Telephone System 8 Mainframe Computer MODEM
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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 5 RS-232 Terminology • DTE (Data Terminal Equipment) vs. DCE (Data Communications Equipment) Al l k • A closer look: Terminal MODEM Telephone System (also called the The “data set” 9 (also called the data link) Is the interface to the data link. It is the communications equipment Source and user of data RS-232 Terminology • DTE vs. DCE Terminal (DTE) MODEM (DCE) Mainframe Telephone System 10 Mainframe Computer (DTE) MODEM (DCE)
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MFET 374, Manufacturing Integration I 2/19/03 The RS-232 Serial Interface 6
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This note was uploaded on 02/29/2012 for the course MFET 374 taught by Professor T.e.kostek during the Spring '10 term at Purdue University-West Lafayette.

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The RS232 Serial Interfacing - MFET 374, Manufacturing...

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