Marconi Instruments 2955 - Page 67

TABLE
3*3
GPIB
SWITCH
SETTINGS
OPERATION
Switch
Sit
Function
Talker/Listener
Talk only
I
4
MS
address
bit
Upper
case
characters only
(for
machines
with
uppercase only)
2
3 Address
bit
Suppress carriage return in
output
(for dedicated
printer
units)
3
2
Address
bit
Not used
4
i
Address
bit Not used
5
'
0
LS
address
bit
Not used
6 5 0
=
lalker/listener
1
=
talk
only
Capability
identification
codes
These are
defined by
IEEE Std.
488-
197S.
The capabilities are
as
follows:-
SH1
:
Source
handshake
(comprete
capadiiity)
The
source handshake
sequences the transmission of each data byte
from
the instrument
over
the
bus data lines.
The
sequence
is
initiated
when the
function
becomes
active,
and
the purpose
of the
function is to
synchronize
the rate
at which
bytes become
available to the
rate
at
which
accepting
devices
on the
bus
can receive the data,
AH1
:
Acceptor
handshake
(complete
capability)
The
acceptor
handshake
sequences
the reading
of the data byte
from
the
bus data
lines,
T5;
Talker
function
(compiete
capability)
The talker
function provides
the
2955
with
the
ability
to send
device
dependent
messages
over
the
bus to other devices.
The
ability
of any
device to talk
exists
only
when it
has
been
designated
as
a talker by the
controller.
TEO:
Extended talker
(no capability)
L4:
Listenerfunction(nojistenoniyfunc:ion)
The
listener function
provides
a device with
the ability to receive
device
dependent
messages
over
the bus.
The ability
of any
device
to
listen exists
only
when it
has been
designated as
a
listener
by
the
eontroiier.
LEO: Extended listener
(no
capability)
SRI;
Servicerequest
function
(complete
capability)
The
scrvhcc
request
function
gives the
2955
the capability
to
Inform
the
controller
W’hen it
requires
attention.
RLl;
Remote/Jocal
function
(complete
capability)
The
remote.'loeai
function
allows
the
2955 to be
controlled either by
the
local
front
panel
keys
or by
device
dependent
messaues
uvu.'’
the
bus.
PPG:
Parallel
poll function
(no
capability)
DC1;
Device
clear
function
(complete cacability)
Device clear
is
a
general
reset
and mav
be
given to all devices in the
system
simultaneously
(
DCL). 2955
resets
to
the
power*up
mode.
DTI;
Device
trigger
function
(complete capability)
Device
trigger
is used
by the
2955 to inmate a
sequential
tone sequence.
CO:
Controllerlunction
(no
capability)
El
:
Open
collector drivers
The
GPIB drivers have
open
collector,
rather than
iri-staie
outputs.
4688I-622N
Apr,
88
3-43