User manual

*WAI — Wait-to-Continue Prevent execution of commands until previous commands are
completed
Description
Two types of device commands exist:
• Sequential commands-A command whose operations are allowed to finish before
the next command is executed.
• Overlapped commands-A command that allows the execution of subsequent com-
mands while device operations of the Overlapped command are still in progress.
Use the *WAI command to suspend the execution of subsequent commands until the de-
vice operations of all previous Overlapped commands are finished. The *WAI command is
not needed for Sequential commands.
The Model 2000 has three overlapped commands:
• :INITiate
• :INITiate:CONTinuous ON
•*TRG
Note: See *OPC, *OPC? and *TRG for more information.
The :INITiate commands remove the Model 2000 from the idle state. The device opera-
tions of :INITiate are not considered complete until the Model 2000 returns to idle. By send-
ing the *WAI command after the :INITiate command, all subsequent commands will not
execute until the Model 2000 goes back into idle.
The *TRG command issues a bus trigger that could be used to provide the arm, scan, and
measure events for the Trigger Model. By sending the *WAI command after the *TRG com-
mand, subsequent commands will not executed until the pointer for the Trigger Model has
finished moving in response to *TRG and has settled at its next state.
Program Fragment
PRINT #1, "output 02; :syst:pres" 'Select defaults
PRINT #1, "output 02; :init:cont off;:abort"
'Place 2000 in idle
PRINT #1, "output 02; :trig:coun 1;sour tim"
'Program for 30 measurements
and
'then stop (idle)
PRINT #1, "output 02; :samp:coun 30"
PRINT #1, "output 02;:init; *wai" 'Start measurements and send
*wai
PRINT #1, "output 02; :data?" 'Query a reading
PRINT #1, "enter 02" 'Get reading after 2000 goes
into idle
LINE INPUT #2, a$ 'Read the reading
PRINT a$ 'Display the reading
2000-900 (J - Aug 2010) BOOK.fm Page 52 Wednesday, October 12, 2011 12:29 PM