Testing the DR11 chain

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On the older Physical Electronics (PHI) surface analysis systems that are still in service the communication between the computer and the electronic units is based on the old DEC (Digital Equipment Corporation) DR11C protocol. In the late 70s and early 80s PHI used DEC PDP11 computers to control their line of Scanning Auger and X-ray Photoelectron (then called ESCA, now called XPS) Spectrometers. They transitioned to Perkin-Elmer 7000 series computers in the early-80s, then the Apollo workstations in the late 80s and finally to IBM-compatible PCs in the 90s. The one thing that all of these computers had in common was that the interface to the electronics was based on the DR11C protocol.

Occasionally an electronic unit in the DR11 chain can have a problem that results in the DR11 data bus being loaded down, which in turn can cause symptoms that indicate failure in another unit that is actually working properly. In these rare cases, a unit may work fine when tested on the bench, but fail when inserted into the DR11C daisy chain on the system.

For PHI systems that have the RBD 147 PC interface unit, it is easy to test the entire daisy chain using the diagnostics in the AugerScan program. Simply connect all of the units in the DR11C chain that you want to test and run the DR11C diagnostics in the Augerscan –System Diagnostics dialog box. DR11D reads in TTL data; DR11 ports A, B, and C all write TTL data out.

It is important to daisy chain only units that are on the same DR11 bus per the AugerScan and AugerMap software assignments. In the example below, all of the units use DR11A. Note that the DR11 male-to-female adapter is used to reverse the DR11 chain before it goes into the RBD 147 DR11D. Whenever testing a DR11 cable or port, the DR11D cable must be reversed 180 degrees from the normal configuration.

DR11 chain with RBD 147 interface unit

Testing the entire DR11 chain lets you know that all of the electronic units in the chain are not loading down the bus, and also that all of the cables have good contact. If the DR11 test fails, then you can test each cable one at a time and then add in one unit at a time until you find the cable or unit that is causing the failure. This can be a very useful technique when troubleshooting a problem where a unit may work fine on the bench but not when installed into the system’s electronics rack.

Here is a link to a detailed procedure on testing the DR11 ports on the RBD 147 PC interface unit  – RBD 147 DR11 Testing


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