Keithley 2002 Getting Started Manual page 74

3-20 IEEE-488 Bus Operation
One-shot triggering
Our older DMMs generally have two types of triggering: one-shot and continuous. In one-
shot, each activation of the selected trigger source causes one reading. In continuous, the DMM
is idle until the trigger source is activated, at which time it begins taking readings at a specified
rate. Typical trigger sources are:
•
•
•
•
Arming the instrument to respond to triggers is implicit in the non-SCPI DMMs. Simply
sending a command to a non-SCPI DMM to change any of the trigger controls causes the instru-
ment to arm itself for triggers.
The SCPI trigger model implemented in the Model 2002 gives you:
•
•
•
Changing any of the settings in the
2002 for triggers.
The following program sets up the Model 2002 to take one reading each time it receives an
external trigger pulse.
'Example program to demonstrate one-shot external triggering
'For QuickBASIC 4.5 and CEC PC488 interface card
'Edit the following line to where the QuickBASIC
'libraries are on your computer
'$INCLUDE: 'c:\qb45\ieeeqb.bi'
'Initialize the CEC interface as address 21
CALL initialize(21, 0)
'Reset controls in INIT, ARM;LAY1, ARM:LAY2, and TRIG subsystems
'and put trigger model in IDLE state
CALL SEND(16, "*rst", status%)
CALL SEND(16, "trig:sour ext;coun inf", status%)
'start everything
CALL SEND(16, "init", status%)
After the Model 2002 receives the
trigger model, waiting for a pulse on the external trigger jack. Each time a pulse arrives on the
external trigger jack, the Model 2002 takes one reading. Because
to
INFinity
mand to put the trigger model in the idle state, disabling triggers until another
mand is sent.
IEEE-488 talk
IEEE-488 Group Execute Trigger (GET)
"X" command
External trigger (rear panel BNC)
Explicit control over the trigger source (the
A two-level control for arming the instrument for triggers.
A way for completely disabling triggers.
, the trigger model never exits from the
subsystem).
TRIGger
subsystem does not automatically arm the Model
TRIGger
command, it stops in the
INITiate
layer. You can send the
TRIGger
layer of the
TRIGger
has been set
TRIGger:COUNt
com-
ABORt
com-
INITiate