Computer-Aided Measurement And Control (CAMAC) is a
standard bus and
modular-crate electronics standard for
data acquisition
Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the ...
and control used in
particle detector
In experimental and applied particle physics, nuclear physics, and nuclear engineering, a particle detector, also known as a radiation detector, is a device used to detect, track, and/or identify ionizing elementary particle, particles, such as t ...
s for
nuclear and
particle physics
Particle physics or high-energy physics is the study of Elementary particle, fundamental particles and fundamental interaction, forces that constitute matter and radiation. The field also studies combinations of elementary particles up to the s ...
and in industry. The bus allows data exchange between plug-in modules (up to 24 in a single crate) and a
crate controller, which then interfaces to a PC or to a VME-CAMAC interface.
The standard was originally defined by the
ESONE Committee as standard EUR 4100 in 1972,
ESONE letter
/ref> and covers the mechanical, electrical, and logical elements of a parallel bus ("dataway") for the plug-in modules. Several standards have been defined for multiple crate systems, including the Parallel Branch Highway definition and Serial Highway definition. Vendor-specific Host/Crate interfaces have also been built.
The CAMAC standard encompasses IEEE standards:
* 583 The base standard
* 683 Block transfer specifications (Q-stop and Q-scan)
* 596 Parallel Branch Highway systems
* 595 Serial highway system
* 726 Real-time Basic for CAMAC
* 675 Auxiliary crate controller specification/support
* 758 FORTRAN subroutines for CAMAC.
Within the , modules are addressed by slot (geographical addressing). The left-most 22 slots are available for application modules while the right-most two slots are dedicated to a crate controller. Within a slot the standard defines 16 subaddresses (0–15). A slot commanded by the controller with one of 32 function codes (0–31). Of these function codes, 0–7 are read functions and will transfer data to the controller from the addressed module, while 16–23 are write function codes which will transfer data from the controller to the module.
In addition to functions that address the module, the following global functions are defined:
* I – Crate inhibit
* Z – Crate zero
* C – Crate clear
The original standard was capable of one 24-bit data transfer every microsecond. Later a revision to the standard was released to support ''short cycles'' which allow a transfer every 450 ns. A follow on upwardly compatible standard ''Fast CAMAC'' allows the crate cycle time to be tuned to the capabilities of the modules in each slot.
The FASTBUS standard was introduced in 1984 as a replacement for CAMAC in large systems.
Backplane physical characteristics
The physical connector on the back of a CAMAC module is a card-edge connector, with a receiving socket on the backplane. Because there are no alignment pins on the socket or connector, there is the possibility of connector misalignment upon module insertion. Therefore, CAMAC modules may NOT be hot-swapped. Many devices are connected to it.
Backplane electrical characteristics
CAMAC shares low-voltage DC power with NIM crates. The crate supplies +6 V, −6 V, +12 V, −12 V, +24 V, and −24 V to all modules.
See also
* Data acquisition
Data acquisition is the process of sampling signals that measure real-world physical conditions and converting the resulting samples into digital numeric values that can be manipulated by a computer. Data acquisition systems, abbreviated by the ...
* LEMO connector standard
* NIM
* VMEbus
* FASTBUS
References
External links
An Introduction to CAMAC
CAMAC on Linux
{{Computer-bus
Experimental particle physics
Computer buses