IEEE-488 Reference
5-21
40 OUTPUT 707;”*SRE 32” ! Unmask event sum-
mary bit (B5) in Ser-
vice Request Enable
Register.
50 OUTPUT 707;”*ESE” ! Program command er-
ror (missing parame-
ter) to generate SRQ.
60 WAIT 1
70 S=SPOLL (707) ! Serial poll 7001.
80 IF BIT (S,6) THEN Service ! Go to Service (line
200).
90 END
200 SUB Service
210 PRINT “B7 B6 B5 B4 B3 ! Identify bits.
B2 B1 B0”
220 FOR I=7 TO 0 STEP -1 ! Loop eight times.
230 PRINT BIT (S,I) ! Display bit values
240 NEXT I
250 SUBEND
Program analysis:
Line 10 Place 7001 in remote.
Line 20 Perform a device clear.
Line 30 Set bit B5 of Standard Event Enable Register.
This unmasks the command error event.
Line 40 Set bit B5 of the Service Request Enable Regis-
ter. This unmasks the event summary message.
Line 50 Send an illegal command in order to generate an
SRQ.
Line 60 Wait for a second to ensure completion of com-
mand execution.
Line 70 If SRQ occurred, bit B6 in Status Byte Register
will be set and program will go to Service sub-
routine.
Line 200 Service subroutine displays the bit values (0 or
to 240 1) of the Status Byte Register. For this example,
bit B5 (ESB) and bit B6 (RQS) will be set.
The actual serial poll sequence is explained in paragraph
5.8.8.
5.7 Trigger Model (IEEE-488 operation)
The following information describes the operation process of
the Model 7001 over the IEEE-488 bus. The flowchart in
Figure 5-12, which summarizes operation over the bus, is
called the Trigger Model. It is called the Trigger Model be-
cause operation is controlled by SCPI commands from the
Trigger subsystem (see paragraph 5.18). Notice that key
SCPI commands are included in the Trigger Model.
Idle and initiate
The instrument is considered to be in the idle state whenever
it is not operating within one of the layers of the Trigger
Model. The front panel ARM indicator is off when the instru-
ment is in the idle state. While in the idle state, the instrument
cannot perform any scan functions. Over the bus, there are
two SCPI commands that can be used to take the instrument
out of the idle state; :INITiate or :INITiate:CONTinuous ON.
Notice that with continuous initiation enabled (:INIT:CONT
ON), the instrument will not remain in the idle state after all
programmed operations are completed. However, the instru-
ment can be returned to the idle state at any time by sending
the *RST command, or the :SYST:PRES command.
Once the instrument is taken out of the idle state, operation
proceeds into the arm layer (Arm Layer 1) of the Trigger
Model.
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