HP 3455A - Page 29

Model 34S5A
Section 111
Figure 3-3. Connecting the Guard.
^CAUTIONH
Guard
should
always
be connected, either to
the instrument LO
terminal
or to a point in
the source
circuit as indicated in Figure
3-3.
If
the guard terminal
is left open, common-
mode voltages may
exceed the LO-io-Guard
breakdown rating
and damage the instru-
ment.
3-48.
REMOTE OPERATION.
3-49.
General.
3-50.
The Model
3455A is remotely controlled
by
means of the Hewlett-Packard
Interface Bus (HP-IB).
The HP-IB is
a
carefully
defined instrumentation
inter-
face which
simplifies the integration
of instruments,
calculators,
and computers into systems.
NOTE
HP-IB is Hewlett-Packard’s implementation
of
IEEE Sid. 488-1975, "Standard Digital
Interface
for
Programmable Instrumenta-
tion.
"
3-5
1 . The capability of a device connected to the Bus is
specified by the interface functions it has. Table 3-2
lists
the Interface Functions included in
the
Model
34S5A.
These functions are also listed above the rear panel HP-
IB
connector (see Figure
3-1).
The number following
the
interface
function
code indicates the particular capabili-
ty of that function as listed
in
Appendix
C of IEEE Std.
488-1975.
Tabls
3-2.
HP-IB Interface Capability.
Code
Inierfsce
Function
SH1 Source Handihske cepebiliiv
AH1 Acceptor Hattdshake Capability
T6
Talker
(basic
talker, serial poll, talk only mode,
unaddiess
to
talk il addressed to listen)
L4
Listener (basic listener, unaddress
to
listen if
addressed
to
talk)
SRI Service Reauesi Capability
RLl Remote/Local Capability
PRO No Parallel Poll Capability
DC1
Device Clear Capability
DTI Device Trigger Capability
CO
No Controller Capability
El
Open Collector
Bus Drivers
Interface Functions provide the means for
a
device
to
receive,
process and send messages
over
the bus.
3-52.
Messages are the means by which devices
ex-
change control and measurement
information. These
messages permit communication and/or control
bet-
ween:
Controller and Device(s)
Device
and
Device(s)
Controller and Controller(s)
Table
3-3
lists the Bus Messages and gives a brief
description of each. The messages are categorized
by
Bus function.
3-53.
Addrns Selaction.
3-54. The
"talk”
and
"listen” addresses of
the
3455A
are selected
by
the INSTRUMENT ADDRESS switch.
This switch
is a
seven section
"Dip”
switch located
on
the rear panel
(sec Figure
3-1).
The
five switches,
labeled
I through 5
are used
to select a unique talk and listen ad-
dress. Figure
3-4
lists the
available
address codes and the
corresponding
switch
settings. The 3455A normally
leaves the factory with
the
switch
set to listen address 6
and talk address
V
(decimal code 54).
3-55.
Talk Only (No Controllar).
The 3455A
may be used to
provide measurement data
to
another device, such as
a
printer, without having a controller on the Bus.
However, the device must be HP-IB compatible. The
talk only
switch must be
set to
the TALK ONLY posi-
tion. In this mode the 3455A will output measurement
3-7