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AIX Versions 3.2 and 4 Asynchronous Communications Guide

64-Port Problem Determination and Troubleshooting

Problems with the 64-port system generally fall into three categories:

This procedure provides a list of actions and suggestions for debugging 64-port Asynchronous Adapter problems on the system unit. Use them to record data or correct the problem before placing a service call.

  1. Before restarting the system with the shutdown command or reset key, check for obvious problems such as a disconnected cable or unplugged device.
  2. Do not work on the system without proper electro-static discharge (ESD) protection.
  3. Do not replace a 16-port concentrator because of a dead port without first having tried to reset the port through a hardware power cycle (shutdown) or software commands. In many cases, replacing the concentrator corrects the problem only because it performs a power cycle which, in this instance, may be the only action necessary.
  4. Do not reconnect cabling without first dissipating possible built-up electrical charges.
  5. Keep a repair log for the system unit. Look for repeat problems or patterns to problems which may help isolate the original source of trouble. This log will help isolate problems with a particular run, concentrator, or device and is invaluable in determining the root cause in a problem environment.

Known Problems with Asynchronous Adapters

Non-Shielded Wire

Any wiring scheme which runs several hundred feet is subject to atmospheric noise through magnetic induction. Shielding of cable grounds this noise and prevents its induction to signal wires. Non-shielded wiring subjects the system to port hangs, equipment damage, and erroneous data.

Corrective Action
Minimum Transient voltage surge suppression (TVSS) devices should be used to minimize noise and over current situations. A TVSS device should be used at both the device and concentrator end of any port having a higher than normal failure rate. Note that it may become necessary to use TVSS devices on all ports of a concentrator if system environmental problems are serious enough. In most cases, a good contact with "earth ground" is ample enough to dissipate high voltage spikes.
Maximum Replace the wiring to meet specification.

Outdoor Wiring Run and/or Frequent Lightning Damage

Any wiring run that is located outdoors is very subject to atmospheric noise or lightning surges through magnetic induction. A direct lightning hit is not necessary to cause system damage.

Corrective Action
Minimum Transient voltage surge suppression (TVSS) devices should be used to minimize noise and over current situations. A TVSS device should be used at both the device and concentrator end of any port having an out-door run.
Maximum All outdoor wiring runs should be inside metal conduit, and the conduit should be grounded.

Concentrator to Device Exceeds 200 ft or 2500 Pico-Farads

Any wiring system that exceeds the rated capacitance is subject to data loss, port hangs, or both.

Corrective Action
Minimum By moving the concentrator closer (within 200 ft) to its devices, you can take advantage of the maximum length of the controller-to-concentrator cable (2500 ft) and reduce the concentrator-to-device cable length.
Maximum If the concentrator is already 2500 ft from the controller, then the 200 ft run will need a booster device.

Thunderstorms and ESD

Lightning strikes pose the greatest hazard to communication equipment circuitry. A lightning strike several miles away can induce voltages in the communication lines that are sufficient to destroy driver/receiver circuits.

Corrective Action

Cables should be adequately shielded while keeping the cable length to a minimum. Transient voltage surge suppression (TVSS) devices must be used if connecting cables out-of-doors between buildings. This should be done even if cabling is buried in the ground or in conduit.

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