14 Introduction To Programming
The optional header SOURCE precedes the current, list, and voltage subsystems (see Figure 3-2). This effectively makes
:CURRENT, :LIST, and :VOLTAGE root-level commands.
Note The optional Agilent 66001 Keyboard does not display optional headers.Moving Among Subsystems
In order to combine commands from different subsystems, you need to be able to restore the active path to the root. You do
this with the root specifier (:). For example, you could clear the output protection and check the status of the Operation
Condition register as follows (see Figure 2-2):
OUTPUT:PROTECTION:CLEAR
STATUS:OPERATION:CONDITION?
By using the root specifier, you could do the same thing in one message:
OUTPUT:PROTECTION:CLEAR;:STATUS:OPERATION:CONDITION?
Note The SCPI parser traverses the command tree as described in Appendix A of the IEEE 488.2 standard.
The "Enhanced Tree Walking Implementation" given in that appendix is not implemented in the power
module.
The following message shows how to combine commands from different subsystems as well as within the same subsystem
(see Figure 3-2):
VOLTAGE:LEVEL 7;PROTECTION 8;:CURRENT:LEVEL 3;MODE LIST
Note the use of the optional header LEVEL to maintain the correct path within the voltage and current subsystems and the
use of the root specifier to move between subsystems.
Including Common Commands
You can combine common commands with system commands in the same message. Treat the common command as a
message unit by separating it with the message unit separator. Common commands do not affect the active header path;
you may insert them anywhere in the message.
VOLT:TRIG 7.5;INIT;*TRG
OUTP OFF;*RCL 2;OUTP ON
SCPI Data Formats
All data programmed to or returned from the power module is ASCII. The data may be numerical or character string.
Numerical Data
Table 2-1 and Table 2-2 summarize the numerical formats.