Agilent Technologies 3458A User Manual page 238

SSAC, SSDC
Examples
238 Chapter 6 Command Reference
is not changed). Later, where you change to another measurement function, the
output format returns to that previously specified. You must use the SINT output
format when sub-sampling and outputting samples directly to the GPIB. You
can, however, use any output format if the samples are first placed in reading
memory (see next remark). To do this, you should enable reading memory
before executing the SSAC or SSDC command (executing SSAC or SSDC does
not change the output format to SINT when reading memory is enabled).
•
When sub-sampling with reading memory enabled, reading memory must be in
FIFO mode, must be empty (executing MEM FIFO clears reading memory),
and the memory format must be SINT prior to the occurrence of the trigger arm
event. If not, the multimeter generates the SETTINGS CONFLICT error when
the trigger arm event occurs and no samples are taken.
•
For sub-sampling, the trigger event and the sample event are ignored (these
events are discussed in Chapter 4). The only triggering events that apply to
sub-sampling are the trigger arm event (TARM command) and the sync source
event.
•
In sub-sampling, samples are taken on more than one period of the input
waveform. When the samples are sent directly to reading memory (MEM
command), the multimeter automatically reconstructs the samples producing a
composite waveform. When the samples are sent to the output buffer, the
controller must use an algorithm to reconstruct the composite waveform.
Parameters for this algorithm are provided by the SSPARM? command.
•
The effective_interval between samples and the total number of samples taken
are specified by the SWEEP command. (You cannot use the NRDGS command
for sub-sampling.) In sub-sampling, the multimeter will use as many periods of
the input signal as necessary to achieve the specified effective_interval. The
minimum effective_interval for sub-sampling is 10 nanoseconds. (Refer to
"Sub-Sampling" in Chapter 5 for a detailed description of the process.)
•
Related Commands: DSAC, DSDC, FUNC, ISCALE?, LEVEL, LFILTER,
MEM FIFO, SLOPE, PRESET FAST, PRESET DIG, SSDC, SSPARM?,
SSRC, SWEEP, TARM
In the following program, the sub-sampled data is sent to reading memory using
the required SINT memory format. The multimeter places the samples in memory
in the corrected order. The samples are then transferred to the controller using the
DREAL output format (when placing sub-sampled data in reading memory first,
you are not restricted to using the SINT output format).
10 OPTION BASE 1
20 REAL Samp(1:200) BUFFER
30 ASSIGN @Dvm TO 722
40 ASSIGN @Samp TO BUFFER Samp(*) !ASSIGN BUFFER
50 OUTPUT @Dvm;"PRESET FAST"
60 OUTPUT @Dvm; "MEM FIF0"
70 OUTPUT @Dvm; "MFORMAT SINT"
80 OUTPUT @Dvm; "OFORMAT DREAL"
!COMPUTER ARRAY NUMBERING STARTS AT 1
!CREATE BUFFER ARRAY
!ASSIGN MULTIMETER ADDRESS
!TARM SYN, TRIG AUTO, DINT FORMATS
!FIRST-IN-FIRST-OUT READING MEMORY
!SINT MEMORY FORMAT
!DOUBLE REAL OUTPUT FORMAT