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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. Refer to
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 HP-IB 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 HP-IB Service Request (SRQ), you can interrupt the
computer when the Scan Complete Bit is set, after a scanning cycle
completes. This allows the controller to do other operations while the
scanning cycle is in progress.
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 HP BASIC as the programming
language. The computer interfaces with an HP E1300A/E1301A mainframe
over HP-IB. The HP-IB select code is 7, the HP-IB primary address is 09,
and the HP-IB secondary address is 15.
Example: Scan
Complete Interrupt
10 OUTPUT 70915;"*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" ! External trigger mode
50 OUTPUT 70915;"SCAN (@100:105)" ! 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 generated by a completed
scanning cycle
110 END
36 Understanding the HP E1366A/E1367A RF Multiplexers Chapter 4