Annex
R&S
®
SGT100A
544
User Manual 1176.8674.02 ─ 07
receive and evaluate the information of all devices. The following standard methods
are used:
●
Service request
(SRQ) initiated by the instrument
●
Serial poll
of all devices in the bus system, initiated by the controller to find out
who sent an SRQ and why
●
Query of a
specific instrument status
by commands
●
Query of the
error queue
Service Request
Under certain circumstances, the instrument can send a service request (SRQ) to the
controller. Usually this service request initiates an interrupt at the controller, to which
the control program can react appropriately. An SRQ is always initiated if one or sev-
eral of bits 2, 4 or 5 of the status byte are set and enabled in the SRE. Each of these
bits combines the information of the error queue or the output buffer. To use the possi-
bilities of the service request effectively, all bits should be set to "1" in the enable regis-
ters SRE and ESE.
Example:
Use command
*OPC
to generate an SRQ .
*ESE 1
- set bit 0 of ESE (Operation Complete)
*SRE 32
- set bit 5 of SRE (ESB).
After its settings have been completed, the instrument generates an SRQ.
The SRQ is the only possibility for the instrument to become active on its own. Each
controller program should set the instrument such that a service request is initiated in
the case of malfunction. The program should react appropriately to the service request.
Serial Poll
In a serial poll, just as with command
*STB
, the status byte of an instrument is queried.
However, the query is realized via interface messages and is thus clearly faster.
The serial poll method is defined in IEEE 488.1 and used to be the only standard pos-
sibility for different instruments to poll the status byte. The method also works for
instruments which do not adhere to SCPI or IEEE 488.2.
The serial poll is mainly used to obtain a fast overview of the state of several instru-
ments connected to the controller.
Query of an instrument status
Each part of any status register can be read using queries. There are two types of
commands:
●
The common commands
*ESR?
,
*IDN?
,
*IST?
,
*STB?
query the higher-level
registers.
●
The commands of the
STATus
system query the SCPI registers
(
STATus:QUEStionable
...)
Remote Control Basics
