Table of Contents
Advertisement
ADDITIONAL INFORMATION
DESCRIPTION OF CAMAC CAMAC modules may be plugged into a CAMAC mainframe
(called Crate in the CAMAC standard) which has up to 25 sta
tions numbered 1 through 25. A station is a slot which accepts
a CAMAC module. Some modules occupy several stations.
The rightmost two stations are reserved for a Crate Interface or
Controller whereas the remainder are Normal Stations used for
instrumentation modules. The purpose of the crate controller is
to issue CAMAC commands to the modules and transfer infor
mation between a computer and the CAMAC modules. It is
the interface between the CAMAC Dataway and a computer.
All CAMAC operations take place over the CAMAC Dataway.
The Dataway is a parallel bus used to transfer all data, the func
tion coding information, and all status information. In a typical
Dataway operation, the crate controller issues a CAMAC com
mand which includes specifying a station number (N), a subad-
dress (A), and function code (F). In response, the module will
generate a valid command accepted (X response) and act on
the command. If this command requires data transfer, the read
(R) or write (W) lines will be used. Note that the terms Read
and Write apply to the crate controller, not the module. For
example, under a read command, the crate controller reads
data contained within a module.
Whenever there is no Dataway operation in progress (indicated
by the absence of the Busy signal) any module may generate a
signal on its individual Look-at-Me line to indicate that it re
quires attention.
There are also three common control signals made available at
all stations: (Z) to Initialize all units, (C) to clear data registers,
and (I) to Inhibit (e.g., data-taking).
Definition of CAMAC
Commands
The CAMAC command consists of signals on the Dataway lines
which specify at least one module (by individual station number
lines), a subsection of the module or modules (by the four sub-
address bus lines, and the function to be performed (by the five
function bus lines). The command signals are maintained for
the full duration of the operation on the Dataway.
Station Number
Each normal station is addressed by a signal on an individual
station number line (N) which comes from a separate pin at the
control station.
Subaddress Codes
Different sections of a module are addressed by signals on four
A bus lines. These signals are decoded in the module to select
one of up to 16 subaddresses, numbered in decimal from A(0)
to A(15).
27
Advertisement
Table of Contents
