Taking a ride on the VME bus

The second talk Thursday morning was by Ron Fox about a small extension that allows experimental physicists (who aren't professional programmers) to control their experiments.

VME bus (VersaModule Eurocard)

• Defined by IEEE 1014-1987 and others
• Physical standard for cards
• Electrical standard for the bus
• Set of protocols for using the bus

Went through a series of slides explaining how the VME-BUS works (arbitration and read cycle).

Bus used in three systems at NSCL:

• Accelerator Control systems
• Experiment Control systems
• Data Taking

The extension is targeted primarily for the experiment control systems.

Extension provides not much:

• Create a slice of memory/map of address space for each of the common address modifiers (A16, A24, A32 and GEO)
• Ability to set/get long words, words or bytes in an arbitrary offset relative to the start of the address map
• Address map boundary protection

package require vme
vme create name -device amod base nbytes
name set {l|w|b} offset value
name get {l|w|b} offset
vme delete name
vme list

All ~500 lines of C++. Various pure Tcl packages built on top.

Showed GUIs that were developed using the package that control experiments.

—Michael A. Cleverly
Thursday, October 12, 2006 at 10:24