Keithley 2750, User Manual

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6-12 Buffer Model 2750 Multimeter/Switch System User’s Manual
j. TRACe:DATA:SELected? <start>, <count> Specify readings to return
TRACe:NEXT? Query location of last buffer reading
Use the TRACe:DATA:SELected? command to specify which stored readings to return. The
<start> parameter specifies the first stored reading to return. Note that the first stored read-
ing in the buffer is #0. The <count> parameter specifies the number of readings to return.
When the storage process is aborted, you can use TRACe:NEXT? to determine the buffer
location for the next stored reading. For example, if the last reading is stored at memory
location #36, TRACe:NEXT? will return the value 37. This query is useful when using the
buffer in the continuous storage mode (TRACe:FEED:CONTrol ALWays) as demonstrated
by the following example:
Example
— Assume the buffer is configured for continuous (wrap-around) storage, and the
buffer size is 100. At some point you stop the storage process and want to return all the read-
ings that were stored since the last time the buffer filled. The following command will return
the buffer location for the next stored reading:
TRACe:NEXT? ' Query buffer location for next stored
reading.
Assume that the above query returned value 37. Now you can use that value as the <count>
parameter for the following command to return the 37 readings (0 through 36):
TRACe:DATA:SELected? 0, 36 ' Return 37 buffer readings
(0 through 36).
NOTE When using the RS-232 interface, the TRAC:DATA:SEL? command should
always be used when recalling more than 100 points of buffer data. For large
buffers, the PC may lose synchronization and data can be lost. To avid this, use
this query command to recall buffer data in 100 point chunks.
k. TRACe:NOTify <NRf> Specify number of readings that will
set Trace Notify bit
<NRf> = 2 to 109999
Use this command to specify the number of stored readings that will set bit B6 (Trace
Notify) of the measurement event register. See
Section 11 for details on status structure.
The maximum valid parameter value for this command is one less than the present buffer
size (which is set by the TRACe:POINTs command). For example, TRACe:POINts 110000
sets the buffer size to 110,000 readings. For this buffer size, the maximum valid parameter
value for TRACe:NOTify is 109999 (110000-1).
When an invalid parameter value is specified, the command is ignored and causes error -222
(parameter data out of range).
2750-900-01.book Page 12 Wednesday, August 3, 2011 7:56 AM