IEEE-488 Reference
4-23
Arm layer1
NOTE
For front panel operation, this layer is
called the arm layer.
In general, the instrument requires an arm event to allow op-
eration to proceed to the next layer (arm layer 2). With the
Immediate control source selected (:ARM:SOURce IMMe-
diate), operation immediately proceeds to the next layer
when the instrument is taken out of the idle state. The *RST
and :SYSTem:PRESet commands also set the arm control
source to Immediate. With one of the other control sources
selected, the instrument will wait until the appropriate event
occurs.
With the Manual control source selected (:ARM :SOURce
MANual), the instrument will wait until the front panel
TRIG key is pressed. Note that the Model 2001 must be tak-
en out of remote (press LOCAL key or send LOCAL 716
over bus) before it will respond to the TRIG key. With the
Bus control source selected (:ARM:SOURce BUS), the in-
strument will wait until a bus trigger (GET or *TRG) is re-
ceived. With the External control source selected
(:ARM:SOURce EXTernal), the instrument will wait until
an input trigger (via EXTERNAL TRIGGER connector on
rear panel) is received. With the Trigger Link control source
selected (:ARM:SOURce TLINk), the instrument will wait
until an input trigger is received (via TRIGGER LINK). With
the Hold control source selected (:ARM:SOURce HOLD),
the instrument will not respond to any of the control source
events.
NOTE
With the Immediate trigger source select-
ed, a “trigger ignored” message will be
displayed if an external trigger is sent to
the Model 2001 or a manual trigger (ie.,
pressing TRIG key) occurs. The external
or manual trigger is not used (ignored).
As can be seen in the flowchart, there are three paths that al-
low operation to loop around the control source. These three
paths are described as follows:
1. When the Source Bypass is enabled (:ARM:TCONfig-
ure:DIRection SOURce) and the External or Trigger
Link control source is selected, operation will loop
around the control source on the initial pass through arm
layer 1. If programmed for another arm (arm count > 1),
the bypass loop will not be in effect even though it will
still be enabled. The Source Bypass loop will reset (be
in effect) if operation goes into Idle.
Enabling the Source Bypass also enables the Output
Trigger. When operation returns to arm layer 1 from arm
layer 2, an output trigger pulse will occur. If the Trigger
Link control source is selected, the output trigger pulse
will be available on the programmed TRIGGER LINK
output line. For all other control source selections, the
output trigger pulse will be available at the METER
COMPLETE connector. The Output Trigger in this lay-
er is disabled when the Source Bypass is disabled
(:ARM :TCONfigure:DIRection ACCeptor).
2. Each time the :ARM:IMMediate command is sent, op-
eration will loop around the arm control source. It is
used when you do not wish to wait for a programmed
arm event to occur (or when the Hold control source is
selected).
3. Each time the :ARM:SIGNal command is sent, opera-
tion will loop around the arm control source. It is used
when you do not wish to wait for a programmed arm
event to occur (or when the Hold control source is se-
lected).
After all other instrument operations have been completed,
the instrument can be returned to arm layer 1 by program-
ming the instrument for additional arms. The :ARM:COUNt
<n>|INFinite command can be used to set the arm count to a
finite value (where n = 1 to 99999) or for an infinite (INF)
number of arms. The *RST and :SYSTem:PRESet com-
mands set the arm count to 1.
After the instrument leaves arm layer 1, operation proceeds
into the scan layer (arm layer 2).
Arm layer2
NOTE
For front panel operation, this layer is
called the scan layer.
In general, the instrument requires a scan event to allow op-
eration to proceed to the next layer (trigger layer). With the
Immediate control source selected (:ARM:LAYer2:SOURce
IMMediate), operation immediately proceeds to the next lay-
er. The *RST and :SYSTem:PRESet commands also set the
scan control source to Immediate. With one of the other con-
trol sources selected, the instrument will wait until the appro-
priate event occurs.
With the Timer control source selected
(:ARM:LAYer2SOURce TIMer), operation will immediate-
ly proceed into the trigger layer on the initial pass through
arm layer 2. Each additional scan will not occur until the pro-
grammed timer interval elapses. The timer can be set to an
interval from 1msec to 999999.999 seconds.
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