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SCPI programming - buffer
Buffer commands are summarized in Table 6-1 . TRACe subsystem commands are used to
store and recall readings in the buffer, and CALCulate2 commands are used to obtain statistics
from the buffer data. Additional information on these commands is provided after the table.
TRACe subsystem — The FEED command controls the source of the readings. With the
SENSe parameter selected, raw input readings are stored in the buffer. With the CALCulate
parameter selected, results of the mX+b or Percent (%) calculation are stored in the buffer.
Commands to control and configure the mX+b and Percent calculations are summarized in
Table 4-2 in Section 4 .
FEED:CONTrol is used to control the storage process. NEXT starts the storage process and
NEVer stops it. After storage is completed, buffer control automatically returns to NEVer.
CALCulate2 subsystem — After the selected statistic is enabled, IMMediate or IMMediate?
must be sent to calculate the statistic from the data in the buffer. The DATA? command does not
initiate a calculate operation. It simply returns the result of the last calculation. If new data is
stored in the buffer, you must again send the IMMediate or IMMediate? to recalculate the
statistic from that new data.
There is no SCPI command to obtain the Peak-to-Peak statistic. To get the Peak-to-Peak
statistic, your program will have to calculate it from the MAX and MIN statistics.
NOTE Since CALC2:IMM and CALC2:IMM? are slow responding when performing the
standard deviation calculation on large buffers, *OPC or *OPC? should be used with
them. Details on *OPC and *OPC? are provided in
Section 12 .
Table 6-1
SCPI commands - buffer
Commands Description Default
:TRACe TRACe Subsystem: See Note
:CLEar Clear readings from buffer.
:FREE? Query bytes available and bytes in use.
:POINts <n> Specify number of readings to store; 2 to 1024.
:FEED <name> Select source of readings; SENSe, CALCulate, or NONE.
:CONTrol <name> Select buffer control mode; NEVer or NEXT.
:DATA? Read all readings in buffer.
:CALCulate2 CALCulate2 Subsystem:
:FORMat <name> Select buffer statistic; MINimum, MAXimum, MEAN,
SDEViation or NONE. NONE
:STATe <b> Enable or disable statistic calculation. OFF
:IMMediate Recalculate raw input data in buffer.
:IMMediate? Perform calculation and read result.
:DATA? Read result of statistic calculation.
Note : SYSTem:PRESet and *RST have no effect on :TRACe commands.
Buffer 6-5