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Using the Scan Complete Bit
You can use the Scan Complete bit (bit 8) in the Operation Status Register
of a switchbox to determine when a scanning cycle completes (no other bits
in the register apply to the switchbox). Bit 8 has a decimal value of 256 and
you can read it directly with the STAT:OPER? command. See the
STATus:OPERation[:EVENt]? command in Chapter 5 for an example.
When enabled by the STAT:OPER:ENAB 256 command, the Scan
Complete bit will be reported as bit 7 of the Status Register. Use the GPIB
Serial Poll or the IEEE 488.2 Common Command *STB? to read the Status
Register.
When bit 7 of the Status Register is enabled by the *SRE 128 Common
Command to assert an GPIB Service Request (SRQ), you can interrupt the
computer when the Scan Complete bit is set, after a scanning cycle
completes. This allows the computer to do other operations while the
scanning cycle is in progress.
Example: Scan
Complete Interrupt
The following example monitors bit 7 in the Status Register to determine
when the scanning cycle completes. The computer used in this example is
an HP 9000 Series 200/300 used with BASIC as the programming language.
The computer interfaces with an Agilent E1300B/E1301B Mainframe over
GPIB. The GPIB select code is 7, the GPIB primary address is 09, and the
GPIB secondary address is 15.
10 OUTPUT 70914; "*CLS" ! Clear all switchbox status
structure
20 OUTPUT 70915; "STAT:OPER:ENAB 256"! Enable Scan Complete Bit to
set bit 7 in Status Register
30 OUTPUT 70915:"*SRE 128" ! Enable bit 7 of Status Register to
assert SRQ
40 OUTPUT 70915;"TRIG:SOUR EXT" ! Set to external trigger mode
50 OUTPUT 70915;"SCAN(@100:147)" ! Select channels to be scanned
60 OUTPUT 70915; "INIT" ! Start scanning cycle
70 WHILE NOT BIT(SPOLL(70915),7) ! Waiting for scan complete
80 PRINT "DO OTHER OPERATION HERE"! Enter program lines for
computer to do other operations
90 END WHILE
100 PRINT "INTERRUPT GENERATED" ! Program goes to this line after
interrupt is generated by a
completed scanning cycle
110 END
38 Understanding the Agilent E1364A Form C Switch Chapter 4