Hp-Ib Interrupts - HP 7470A Interfacing And Programming Manual

10 PRINTER IS ?o5,0o
2O OPTION BHSE 1
30 INTEGERX(5OOJ,Y(5OOJ,P(500)
40 FOR c=1 TO 500
so PRINT "DP;"
so DISP "ENTER POINT ";c
?o GUSUB 150
so PRINT "UD;"
so ENTER?0S ; X(C),Y(C),PECJ
100 NEXT c
110 PRINTER IS 2
120 FOR c=1 TO 500
130 PRINT X(CJ;Y(CJ;P(CJ
140 NEXT c
150 STOP
150 ! Check SUBRUUTINE
170 PRINT "US;"
180 ENTER ?o5 ; 5
190 S=INT(S/4)
200 IF S=INT(S/2)*2 THEN 1?0
210 RETURN
220 END
HP-IB Interrupts and Polling
A third method can be used by advanced programmers thoroughly
familiar with the HP-IB interface, polling techniques, and interrupts. It
should only be used when the computer can perform useful tasks while
waiting for the digitized point to be entered. This method involves
setting a value of 4 in the S-mask of the IM command, e.g., IM 223,4 ,0;
to cause the plotter to generate an RQS (service request) when a
digitized point is available. With an interrupt routine enabled for
service requests, the computer can send a DP command to initiate
digitizing, and then proceed with some other task until the digitized
point is entered. When the point is available, the computer is interrupted
by the RQS, and program execution branches to the routine to process
the digitized data. This routine could simply send an OD command and
read the digitized point, or it could perform bit checking of the plotter
status byte if multiple S-mask values have been specified to generate
the RQS. The status byte can be obtained by serial polling or simply by
sending an OS command. Because interrupts and polling are highly
machine—dependentand beyond the scope of this manual, no examples
are given.
DIGITIZING 6-7