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Acquisition systems
VME-CAEN
FO C SA NEANU
M A R IN
DFNA
Summary
Standard VMA
Data acquisition
VMEbus components:
 VME Controller
 ADC
 QDC
 TDC
CAENVMElib
Standard VME
o VMEbus (VersaModular Eurocard bus) is
a bus (computer data path) system
o Designed by Motorola
o Used in industrial, commercial, and military
applications worldwide.
Standard VME
A VMEbus system is based on the VME standard.
The VME standard defines the mechanical specifications such as:
◦ board dimensions
◦ connector specifications
◦ enclosure characteristics
◦ the electronic specifications
◦ signal functions
◦ timing
◦ signal voltage levels
◦ and master/slave configurations.
Data acquisition
• Master / slave architecture
Functional unit called
•
Data
Functional unit called
MASTER
SLAVE
Initiates transactions
Responds to transactions
Since multiple Masters can reside on the bus, it is a MULTIPROCESSING bus
VME Components
VME Controller – V1718
VMEBus module
o The V1718 is a VME to USB 2.0 Bridge,
housed in a 1-unit wide VME 6U module.
o The unit acts as a VME Master module
and can be operated from the USB port
of a standard PC.
o The board can operate as VME System
Controller
VME Controller
As a system controller a VMEbus system has four subbuses:
◦
◦
◦
◦
the arbitration bus,
the data transfer bus,
the priority interrupt bus,
and the utility bus.
ADC CAEN V785N VMEBus
module
o
The Model V785 N is a 1-unit wide
VME 6U module housing 16 Peak Sensing
Analog-to-Digital Conversion(ADC)channels.
o
The peak values are converted into
voltage levels by the Peak Sensing sections and then
multiplexed and converted by two fast 12bit
ADC modules.
o
The ADCs use a sliding scale technique
Peak sensing
Analog to digital conversion
Sliding scale technique
QDC CAEN V792 N VMEbus
module
o This model is a 1-unit wide VME 6U module
housing 16 Charge-To-Digital Conversion channels
(QDS)
o The integrated currents are converted into voltage
levels by the QAC sections , multiplexed and
converted by two fast 12-bit ADC modules.
TDC CAEN V1290 VMEbus
module
o This module is a 32 channel Multihit Time-To-Digital
Conversion (TDC), housed in a 1-unit wide VME
6U module.
o TDC is a device for recognizing events and providing a
digital representation of the time they occurred.
The data acquisition can be programmed in "EVENTS" :
1.
TRIGGER MATCHING MODE
2.
CONTINUOUS STORAGE MODE.
TRIGGER MATCHING MODE
o
o
o
o
match window
window offset
extra search margin
reject margin.
CONTINUOUS STORAGE
MODE
o In this readout mode the data loaded are straightly
forwarded into the Readout FIFO.
CAENVMELib Library
o Open (Init) and Close the communication and the
devices
o
CAENVMELib Library
o Make single Read cycles
o Make Block Transfer Read/Write
cycles
CONCLUSION
o The VME DAQ in the current form provides us with a powerful
system because of the large number of parameters which can be
acquired simultaneously and its ability to handle high event rates.
References:
1.
VME Data Acquisition System: Fundamentals and Beyond, Abhinav
Kumar Bhabha Atomic Research Centre, Mumbai, March 2011.
2.
Development of data acquisition software for VME based systems,
A. Kumar, A. Chatterjee, K. Mahata, K. Ramachandran, BARC,
Mumbai, India, 2012.
3.
Nuclear lectures , Michigan State University
4.
What is vmebus basics tutorial, Ian Pool
5.
www.caen.it