Status Subsystem
Introduction
Status reporting is a method to let the
controller know what the counter is do
-
ing. You can ask the counter what status
it is in whenever you want to know.
You can select some conditions in the
counter that should be reported in the Sta-
tus Byte Register. You can also select if
some bits in the Status Byte should gen-
erate a Service Request (SRQ).
(An SRQ is the instrument’s way to call
the controller for help.)
Status Reporting Model
n
The Status Structure
The status reporting model used is stan
-
dardized in IEEE 488.2 and SCPI, so
you will find similar status reporting in
most modern instruments. Figure 6-6
shows an overview of the complete status
register structure. It has four registers,
two queues, and a status byte:
–
The Standard Event Register reports the
standardized IEEE 488.2 errors and condi
-
tions.
–
The Operation Status Register reports the
status of the measurement cycle (see also
ARM-TRIG model, page 6-23).
–
The Questionable Data Register reports
when the output data from the counter may
not be trusted.
–
The Device Register 0 reports when the
measuring result has exceeded prepro-
grammed limits.
–
The Output Queue status reports if there
is output data to be fetched.
– The Error Queue status reports if there
are error messages available in the error
queue.
–
The Status Byte contains eight bits. Each
bit shows if there is information to be
fetched in the above described registers
and queues of the status structure.
Using the Registers
Each status register monitors several con
-
ditions at once. If something happens to
any one of the monitored conditions, a
summary bit is set true in the Status Byte
Register.
Enable registers are available so that you
can select what conditions should be re
-
ported in the status byte, and what bits in
the status byte should cause SRQ.
+
A register bit is TRUE, i.e., some
-
thing has happened, when it is
set to 1. It is FALSE when set to
0.
6-10 Status Subsystem
Using the Subsystems
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