Modular crate electronics: Difference between revisions

Revision as of 00:43, 17 May 2017

Revision as of 22:32, 25 May 2017

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Some modules just draw power from the backplane connectors and have all of their data inputs and outputs on the front plate. Other modules take inputs or controls to and from the backplane or have their behavior controlled from the backplane. Some types of modules have active circuitry inside them, and act almost as small computers; others are not stateful at all and are only dumb single components.

== Types of Cratecrate Systemssystems ==

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

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=== 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]]ped, 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]]pable. The CAMAC backplane contains a signaling 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]]<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> is a crate/module standard developed later than the other two for high-speed parallel data acquisition. Rather than individual components, FASTBUS modules tend to be data acquisition modules with many input connectors on the front, while the stored data is read out on the backplane. The connectors on the back of a FASTBUS module are 2two parallel pin sockets on the module and pins sticking out of the backplane. The main connector in a fastbusFASTBUS crate covers about the bottom 2/3 of the module. There is also an upper connector that consists of pass-through pins to the back side of the backplane; this allows custom modules to be plugged in there.

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

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