The Fieldbus and DeviceNet standards are also becoming a standard at the field and instrumentation level, and are replacing the traditional approaches in the plant today. Ethernet is fast becoming the obvious choice for industrial control networking worldwide. While the basic structure of Ethernet has not changed much, the faster technologies such as fast Ethernet and gigabit Ethernet have increased the complexity and choices you have available in planning and designing these systems. There has also been a convergence between Fieldbus and DeviceNet standards in that they are also increasingly becoming based on industrial Ethernet for the higher speed data transfer applications. There is a fair degree of confusion about where Fieldbus, DeviceNet and Ethernet, are applied and the workshop commences with a clear comparison between the different standards and where they are applied. The first day focuses on AsiBus, DeviceNet, Profibus and Foundation Fieldbus technologies in a simple and understandable manner. A detailed discussion is conducted on the application of these technologies in your plant today. There are many misconceptions on the best standard to apply in a given section of the plant. This workshop will promote the theme which is rapidly growing strength, in that you should focus on your application and apply the particular Fieldbus or DeviceNet to match this application and ensure easy interconnectivity between the different standards. Picking one standard to match all applications is not really a practical approach. Ethernet is then discussed with a brief outline of the fundamentals of Ethernet and its operation. The method of access is discussed in depth, and topics such as full duplex and auto negotiation are explained. The best methods of designing and installing the cabling systems are explored with the discussion ranging from 10Base-T over twisted pair to gigabit Ethernet cabling methods of optimising Ethernet to obtain the best performance are also defined.

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Practical Troubleshooting & Problem
Solving of Ethernet Networks:
RS-232 Fundamentals

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DTE vs DCE
• DTE
– Data Terminal Equipment
– Transmits on Pin 2 for 25-pin connector
• DCE
– Data Communications Equipment
– Transmits on Pin 3 for 25-pin connector

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RS-232 Connections (DB25)

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EIA-232
• Electrical Signal levels
– Logic 0 =+3 to+25V = Control ON
– Logic 1 = -3 to -25V = Control OFF
• Mechanical Interface
– DB-25, DB-9 connectors
• Circuit Functionality

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Voltage Levels for EIA-232
Data Line Driver
Control Line Driver
0 (Space)
1 (On)
1 (Mark)
0 (Off)
Data Lines
Driver Receiver
Control Lines
Data Receiver
Control Receiver
+25 V
+25 V
+25 V
+25 V
-25 V
-25 V
-25 V
-25 V
+5 V
+5 V
+3 V
+3 V
-5 V
-5 V
-3 V
-3 V
0 V
0 V
0 V
0 V
ON
OFF
0
1

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Pin Assignments
Pin Number
(DTE)
DB9
ConnectorIBM Assignment
DB25 Connector
EIA-232 Pin Assignment
1 Received Line Signal Shield
2 Received Data Transmitted Data
3 Transmitted Data Received Data
4 DTE Ready Request to Send
5 Signal Common/Ground Clear to Send
6 DCE Ready DCE Ready
7 Request to Send Signal Common/Ground
8 Clear to Send Received Line Signal
9 Ring Indicator + Voltage (Testing)
20 - DTE Ready
22 - Ring Indicator

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Limitations
• Point-to-Point
• Distance Limitation
= 2500pf (50ft @ 50pf/ft)
• 20kbps
• -3 to -25V and +3 to +25 V
• Note Table 2.1 Page 30 !

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Typical Approach
• Check basic Parameters
• Identify which is DTE and DCE
• Clarify handshaking compatibility
– either Hardware
– or Software
• Check actual protocol
– use protocol analyzer

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Test Equipment
• Multimeter
• LED
• Breakout Box
• PC Based Protocol Analyzer
• Dedicated Protocol Analyzer

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Breakout Box
LEDs usually Bi-Color
Red commonly Positive Green commonly Negative
DIP
Switches
Common

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RS-232 Breakout Box

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Protocol Analyzer Connections
Protocol
Analyzer

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Typical RS-232 Problems
• Mechanical Problems
– Keep wires short
– Stranded wire instead of solid wire
– Only one wire soldered per pin
– Bare wire should not be visible
– Back shell must secure wire

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Typical RS-232 Problems
• Setup Problems
– Software setup compatible
• 8N1or 7E1 or 7O1
– Baud rate correct
– Code correct - Binary/Hex or ASCII
– Software set up for handshaking
• Hardware or Software control

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Typical RS-232 Problems
• Noise Problems
– Ground Induced Noise
– Induced Noise on TX or RX lines
– Induced noise on Control Lines

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