Operating instructions

Language Dictionary
30
Common Commands
Introduction
Common commands are defined by the IEEE 488.2 standard to perform some of the basic instrument functions, such as
identification, reset, determining how status is read and cleared, and how commands and queries are processed. Common
commands are accepted and processed when they are sent as separate commands and also when they are included within
program messages. Execution of a common command does not change the position of the parser in the program tree but
leaves it in the same place it was before the common command was executed (refer to Chapter 2 -Introduction to HPSL).
This does not mean that a common command has no effect on the rest of a programming message.
The electronic loads respond to the 13 required common commands that control internal operation, synchronization, status
and event registers, and system data. Because they have full trigger capability, the electronic loads also respond to *TRG.
In addition, the electronic loads accept six optional common commands. The description for each common command or
query specifies if it affects status registers. In order to make use of this information, you must refer to Chapter 5 - Status
Reporting, which explains how to read the status registers and use the information that they return.
Order of Presentation
Figure 4-1 shows the common commands and queries, which are presented in alphabetical order. If a command has a
corresponding query that simply returns the data or status specified by the command, then both command and query are
included under the explanation for the command. If a query does not have a corresponding command or is functionally
different from the command, then the query is listed separately.
*CLS Clear Status Command
Type
Device Status
Description
This command causes the following actions (See Chapter 5 - Status Reporting for
descriptions of all registers):
•
Clears the following registers without affecting any corresponding Enable registers or
Transition Filters:
 Channel Status Event registers for all channels.
 Channel Summary Event register.
 Questionable Status Event register.
 Standard Event Status Event register.
 Operation Status Event register.
•
Clears the Error Queue.
•
Forces a previously executed *OPC command to appear as if it had been completed.
It does not do this with the *OPC? command. (See *OPC? for more details).
• If *CLS immediately follows a program message terminator (<nl>), then the output
queue and the MAV bit are also cleared.
Command Syntax
*CLS
Parameters
None
Query Syntax
*OPC *OPC?