Remote Programming
SERVICE REQUESTS
interface messages described here originate at the con-
SPD Serial Poll Disable
-
A multiline mbge
troller.
which removes the serial
poll
enable state.
3-53.
Address
Messages
Address messages are used by the controller to communi-
cate talk and listen control to other devices on the
bus.
Address messages are sent over the eight
data
lines of the
bus
while the controller holds ATN true. Address mes-
sages are processed immediately and are not placed in the
input buffer. The address messages are:
MLA
My Listen Address
-
Addresses
a
device to
listen
SPE
Serial Poll
Enable
--
A multiline message
which causes the serial poll
data
(rathe~i than
butput buffer
data)
to
be
transferred on
tye
bus
once ATN becomes false.
3-55.
Addressed Commands
Addressed commands are multiline messages which are
accepted
ankl
interpreted
by
only those devices dentlY
addressed tb
listen.
The 8840A responds to the folldwing
addressed commands:
I
MTA My Talk Address
--
Addresses a device to
talk
GET
UNL Unlisten
--
Addresses all listeners to unlisten
UNT
Untalk
-
Addresses dl talkers to untalk
3-54.
Universal
Commands
Universal commands are accepted and interpreted by all
devices
on the bus. The commancls are of two types,
multiline messages and uniline messages. Multiline mes-
sages are sent over the eight parallel data lines
in
the
IEEE-488 bus. Uniline messages are sent over one of
the
GTL
individual interface management lines in the IEEE-488
bus.
All universal
commands
except DCL are processed
immediately by the
88404
ahead of any device-dependent
commands. Only DCL enters the 8840A input buffer.
Group Execute Trigger
-
(Not to
be
codfused
with the devicedependent
Get
comm;inds.)
GET loads
a
trimer command into
the
input
buffer and also terminates the string at that
point. Only a single character is loaded into
the
itlput buffer. The trigger commqd is
executed in its proper
turn
in the input qtring,
rather than immedjately. When executed, GET
initiates
a
measurkment
.
Go To
Local
--
Causes
the 8840A to switch to
local. This command
does
not enter the input
buffer. If the display has been blanked (dith a
bl
command), issue a DO command defore
sending
GTL.
Am
IFC
REN
DCL
The 8840A responds to the following universal messages:
SDC
Selected Device Clear
--
Identical td the
universal command
DCL,
but is
accept4
and
Attention
--
A uniline message which causes interpreted by current listeners only. Therefore,
the 8840A to interpret multiline messages as it clears the 884049 only if it is
ad&&
to
interface messages
(AD,
AC, or UC).
When
listen.
false,
multiline messages are inte~preted
as
device-dependent messages.
3-56.
TALK-ONLY
MODE
The talk-only mode. lets you take advantage of the remote
Interface
--
A
unihne
marage
which
Wlity of the 8840A witht having to use
i$@u-
Only
the
interface
the
ment contrdller. To
put
the
8840A
in the talk-only
wade:
placing it in
a
known quiescent state.
Remote Enable
--
A uniline message which,
1.
Turn *e 8840A POWER switch OFF.
when received with
MLA,
switches the
8840A
2.
Set
the rear panel TALK ONLY bit switch to
1
(the
to remote. When REN is set false, the 8840A
up position).
switches to local and removes local lockout.
3.
Connect
the
8840A
via the 1EEE-488
bus
to your
Device Clear
--
A multiline message which is
printer, data logger, or other device.
loaded into the input buffer
as
a special
4.
Cmfiwe
the
other
device
as
a
listern,
device-clear command. DCL performs the
same operation as the device-dependent com-
5.
Turn the 8840A POWER switch ON.
marid
*'
that
it
is
before
any
Other
6.
Configure the
8WA
with the front panel co~)trols.
characters that are already preqnt in the input
and
'lean
the
entire
*
buffer'
The 8840A reads the TALK ONLY bit switgh on
cessing then continues normally. The action of
power-up and when it receives the interface codnand
DCL
is
immdate;
if
the
wA
is
taldng
EC.
You
therefore set the TALK ONLY
suit&
to
1
a
rrading
when
DCL
is
reoeiveQ
the
DCL
after powerpup as long
as
you then send the
884QA
the
command
is
executed after the measurement is
IFC
commrind.
finished.
I
LLO
Local
Lockout
--
A multiline message which
3-57.
REMOTE CAUBwTlON
disables the front panel LOCAL button. The
The 8840A can
be
calibrated over the IEEE-488 bus~using
result
is
that the local mode is not accessible
remote conlmands. Refer to the Maintenance section for
by front panel control. details.
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