User`s manual

46 Understanding the Relay Multiplexer Modules Chapter 4
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 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 a GPIB Service Request (SRQ), you can
interrupt the controller 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 the example is an
HP Series 200/300 used with BASIC as the program language. The
computer interfaces with the mainframe over GPIB. The GPIB select code
is 7, the GPIB primary address is 09, and the GPIB secondary address
is 14.
Example: Scan Complete
Interrupt
10 OUTPUT 70914;"*CLS"
!Clear all switchbox status
structure.
20 OUTPUT 70914;"STAT:OPER:ENAB 256"
!Enable Scan Complete Bit to set
bit 7 in Status Register.
30 OUTPUT 70914;"*SRE 128"
!Enable bit 7 of Status Register
to assert SRQ.
40 OUTPUT 70914;"TRIG:SOUR EXT"
!Set to external trigger mode.
50 OUTPUT 70914;"SCAN (@100:115)"
!Select channels to be scanned.
60 OUTPUT 70914;"INIT"
!Start scanning cycle.
70 WHILE NOT BIT(SPOLL(70914),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