prog.book : chapter1.fm 76 Mon Feb 15 09:24:37 1999
Power Meter Remote Operation
Status Reporting
1-76 HP E4418B/E4419B Programming Guide
The SRQ Method
When a bit of the Status Register is set and has been enabled to assert
SRQ (*SRE command), the power meter sets the HP-IB SRQ line true.
This interrupt can be used to interrupt your program to suspend its
current operation and find out what service the power meter requires.
(Refer to your computer and language manuals for information on how to
program the computer to respond to the interrupt).
To allow any of the Status Register bits to set the SRQ line true, you have
to enable the appropriate bit(s) with the *SRE command. For example,
suppose your application requires an interrupt whenever a message is
available in the output queue (Status Register bit 4, decimal weight 16).
To enable bit 4 to assert SRQ, you use the following command:
*SRE 16
Note You can determine which bits are enabled in the Status Register
using *SRE?. This command returns the decimal weighted sum of
all the bits.
Procedure
• Send a bus device clear message.
• Clear the event registers with the *CLS (clear status) command.
• Set the *ESE (standard event register) and *SRE (status byte
register) enable masks.
• Enable your bus controller’s IEEE-488 SRQ interrupt.
Examples
The following two examples are written in HP BASIC and illustrate
possible uses for SRQ. In both cases , it is assumed that the meter has
been zeroed and calibrated.
Example 1:
10 ! Program to generate an SRQ when a channel A sensor
20 ! connect or disconnect occurs
30 !
40 ASSIGN @Pm TO 713 ! Power meter HPIB address
50 ON ON INTR 7 GOTO Srq_i! Define service request handler
60 CLEAR @Pm ! Selective device clear
70 OUTPUT @Pm;”*CLS;*RST” ! Clear registers and reset meter
80 !
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