Formats and Data Flow 7
Keysight 53220A/53230A User’s Guide 253
FETCh? - is used following INITiate:IMMediate. After all measurements
specified by TRIGger:COUNt and SAMPle:COUNt are complete, FETCh? transfers
the readings from reading memory to the output buffer. Since read ing memory is
not erased by this action, readings can be “fetched” from memory multiple times.
If there are no readings available or measurements in progress when a “fetch” is
performed, err -230, “Data corrupt or stale” is generated.
If the data format is REAL (FORMat subsystem), each block of readings fetched by
FETCh? is preceded by an IEEE 488.2 Indefinite-Length Block header (Table 7-1).
When sending multiple commands in a single command string, FETCh? should
always be the last command in the string.
FETCh? example
// frequency meas of 500 kHz signal with uHz resolution
CONF:FREQ 500E3, 1E-6, (@1) // configure counter
TRIG:COUN 1 // set trigger count
SAMP:COUN 10 // take 10 readings
INIT:IMM // initiate counter to start rdgs
FETC? // fetch rdgs from memory when complete
R? [<max_count>] - is used following INITiate:IMMediate. Transfers all,
or up to the specified max_count number of readings to the output buffer and
erases those readings (beginning with the oldest) in reading memory.
Unlike FETCh?, R? can be used to transfer readings before the total reading
count is reached (TRIGger:COUNt x SAMPle:COUNt) to prevent a memory
overflow. If there are no readings available or measurements in progress when
“R?” is sent, err -230, “Data corrupt or stale” is generated.
Readings are transferred in Definite-Length Block format (Table 7-1), whether in
ASCII or REAL (binary) format (FORMat subsystem). The ‘oldest’ reading is
transferred first (first in - first out).
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