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24 Reviewing SCPI Syntax Rules
Combine commands from different subsystems
You can send commands and program queries from dif-
ferent subsystems on the same line. Simply precede the
new subsystem by a semicolon followed by a colon. In
the following example, the colon and semicolon pair
before DISP allows you to send a command from
another subsystem.
OUTPUT 720;”:CALC2:PEXC 12;:DISP:WIND:GRAP:STAT OFF”
Sending common commands
If a subsystem has been selected and a common com-
mand is received by the instrument, the instrument
remains in the selected subsystem. For example, if the
program message
”DISPLAY:MARK:MAX:LEFT;*CLS;DISP:MARK:MAX:RIGH”
is received by the instrument, the Display subsystem
remains selected.
If some other type of command is received within a pro-
gram message, you must reenter the original subsystem
after the command.
Adding parameters to a command
Many commands have parameters that specify an
option. Use a space character to separate the parameter
from the command as shown in the following line:
OUTPUT 720;”:INIT:CONT ON”
Separate multiple parameters with a comma (,). Spaces
can be added around the commas to improve readabil-
ity.
OUTPUT 720;”:MEAS:SCAL:POW:FREQ? 1300, MAX”
White space
White space is defined to be one or more characters
from the ASCII set of 0 through 32 decimal, excluding
10 (NL). White space is usually optional, and can be
used to increase the readability of a program.
Numbers
All numbers are expected to be strings of ASCII charac-
ters. Thus, when sending the number 9, you would send
a byte representing the ASCII code for the character “9”
(which is 57). A three-digit number like 102 would take
up three bytes (ASCII codes 49, 48, and 50). This is
taken care of automatically when you include the entire