Product Manual

7526A
Users Manual
5-8
Command Use
Communications between the controller and the Product use commands, queries, and
interface messages. Although the commands use the 488.2 standard as their basis, they
can be used on the IEEE-488 or RS-232 interface. There are some special RS-232 only
commands as shown in the section “Commands for RS-232 Only”.
For more information on IEEE command structures, see the IEEE 488.2 standard.
See Chapter 6 for more information about the commands referenced in this section.
All commands, units, and text data can be recorded in UPPER or lower-case letters. The
Product changes all lower-case letters to upper case before they are used.
Types of Commands
The commands for the Product can be put into these categories:
Device-Dependent Commands
Device-dependent commands are unique to the Product. An example of a device-
dependent command is:
OUT 1 V
This command tells the Product to source 1 V dc
1. Common Commands
Common commands are specified by the IEEE 488.2 standard and are common to
most bus devices. Common commands start with an asterisk (*). Common commands
are available if you use the IEEE-488 or RS-232 interface for remote control. An
example of a common command is:
*IDN?
This command tells the Product to show the instrument identification string.
2. Query Commands
Query commands requests for information, which can be shown as the command
operates, or can be put in a buffer until it is necessary later. Query commands end
with a question mark. An example of a query commands is:
RANGE?
This command tells the Product to show the current DC voltage output range.
3. Interface Messages (IEEE-488)
Interface messages control traffic on the IEEE-488 interface bus. Device addressing
and clearing, data handshaking, and commands to put status bytes on the bus are all
directed by interface messages. Some of the interface messages occur as state
transitions of dedicated control lines. The remaining interface messages are sent
through the data lines with the ATN signal true. All device-dependent and common
commands are sent through the data lines with the ATN signal false.
An important thing about interface messages is that, unlike device-dependent and
common commands, interface messages are not sent literally in a direct method.
They are changed to parallel signal levels on the bus data and control lines.
IEEE-488 standards define interface messages which are managed automatically in
most cases.