13.3. PC Based Systems 729
13.2.DFASTBUSStandard
FASTBUS was originally developed in 1986 jointly by the U.S. NIM and the Euro-
pean ESONE committees. The main motivation of its development was to introduce
capabilities that were not available in the NIM system. Just like the original VME
architecture, the FASTBUS standard supports 32 bit data transfer and addressing.
The bussed architectures allows it to be directly linked to a computer for control
and data handling. The distinguishing feature of FASTBUS is its use of multiple
processor buses linked together in parallel.
D.1 FASTBUSLayout
A standard FASTBUS crate has 26 slots. The user should compare this number with
the standard VME crate that can have a maximum of 21 slots. The larger number of
slots in a FASTBUS crate is due to its compactness and density. In fact this feature
of FASTBUS makes it fairly cost effective as compared to other architectures.
One of the slots in a typical FASTBUS crate is occupied by the so called Geo-
graphical Address and Control card or GAC. This card is generally installed in the
last slot but can also go into 25th slot. Another card that is an integral part of a
complete FASTBUS system is the Arbitration Timing Control card or ATC. The
ATC can occupy the first or the second slot in the crate.
Unlike most of the other architectures, power supply is not an integral part of a
FASTBUS crate. The power requirements of FASTBUS modules therefore dictate
the installation of the proper power supply. The FASTBUS standard specifies the
use of +5V,-5.2V,-2V,± 15 V,and± 28 Vpower supplies.
D.2 FASTBUSBackplane
A FASTBUS backplane consists of two distinct parts, namelysegmentandauxiliary
units. The auxiliary backplane is generally not used for data transfer and is reserved
for implementing custom features. The main data transfer and addressing is done
over the segment backplane. The timing signals needed for addressing and arbitra-
tion are provided by the ATC. The GAC, installed on the other side of the crate,
terminates the signal lines. Its main purpose is to establish communication between
a slot’s slave and a master. The GAC can address individual slots by broadcasting
their hardwired geographic addresses.
13.3PCBasedSystems
A new trend in data acquisition is to employ PC based modules. These modules can
be directly connected to a PC and generally provide a complete solution including
analog processing of the input signals. In this section we will briefly discuss such
solutions.
13.3.APCIBoards............................
Since most PCs have at least one PCI bus slot available, one can build a data ac-
quisition system by installing a signal conditioning unit into this slot. Such modules