Modular crate electronics: Difference between revisions

Revision as of 15:51, 21 September 2013

Revision as of 16:28, 22 September 2013

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There are four main types of modular crate electronic systems used on particle physics experiments.

==== NIM ====

The earliest and simplest crate module standard is the [[Nuclear Instrumentation Module|NIM (Nuclear Instrumentation Module) ]] standard. A NIM crate only has power on the backplane, there is no data bus or data connectors. The NIM backplane connector is an irregular arrangement of individual pins into sockets in the crate. NIM modules typically have multiple single logic blocks on the front with both inputs and outputs on the front panel. A typical NIM module might be, say, four discriminators on the front panel, or three AND gates. NIM modules can be [[hot swap|hot swapped]], since there are no data connectors at the back.

==== CAMAC ====

A later crate standard is [[Computer Automated Measurement and Control|Computer Automated Measurement and Control, or CAMAC]].<ref>{{cite web|title=AN INTRODUCTION TO CAMAC|url=http://www-esd.fnal.gov/esd/catalog/intro/introcam.htm|publisher=FNAL|accessdate=21 September 2013}}</ref> . CAMAC modules are much thinner than NIM modules. The backplane connector of a CAMAC module is a card-edge connector; because of the possibilities of mis-aligning the connectors upon plugin, CAMAC modules are NOT [[hot swap|hot swappable]]. The CAMAC backplane contains a signally protocol for the crate controller to set the values of registers in modules (for configuration) and to read values of registers (for data acquisition). Due to the slowness of the data communication along the backplane, once FASTBUS was invented, CAMAC modules were mostly used for modules that needed to be computer-configured but not for data acquisition.

==== FASTBUS ====

[[FASTBUS|FASTBUS]]<ref name="FNAL intro to Fastbus">{{cite web|title=AN INTRODUCTION TO FASTBUS|url=http://www-esd.fnal.gov/esd/catalog/intro/introfb.htm|publisher=FNAL|accessdate=21 September 2013}}</ref> was a crate/module standard developed later than the other two for high-speed parallel data acquisition. Rather than individual components, FASTBUS modules tended to be data acquisition modules with lots of input connectors on the front, and then the stored data would be read out on the backplane. The connectors on the back of a FASTBUS module were 2 parallel pin sockets on the module and pins sticking out of the backplane. The main connector in a fastbus crate covered about the bottom 2/3 of the module. There was also an upper connector that was merely pass-through pins to the back side of the backplane; this allowed custom modules to be plugged in there.

Fastbus modules are much taller than the other types of crate modules, so the crates are correspondingly taller.

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The FASTBUS backplane was a full data bus where any module could negotiate to be master of the bus to send or receive data.

==== VME ====

[[VMEbus|VME]] (VMEbus) was a bus originally designed to provide an expansion bus for the Motorolla 68000 series processor, but it also became a module electronics crate standard. The first editions of VME were three pins wide with pin sockets on the modules and pins on the backplane. In later editions of the physical standard expanded the connectors with two more rows of pins/sockets on the edges for grounding.