R?

Syntax | Description | Parameters | Remarks | Return Format | Example

Syntax

R? [<max_count>]

Description

This command reads and erases readings from volatile memory up to the specified <max_count>. The readings are erased from memory starting with the oldest (not the most recent) reading first. The purpose of this command is to allow you to periodically remove readings from memory that would normally cause reading memory to overflow (for example, during a scan with an infinite scan count).   

Parameters

Name	Type	Range of Values	Default Value
<max_count>	Numeric	Maximum number of readings to be read and erased from memory.	Erase all stored readings

Remarks

• This command is a special version of the DATA:REMove? command with faster execution time. You can read memory at any time using the R? command, even during a scan.

• Readings can be acquired during a scan using the multiplexer and digital modules or by the internal DMM independently (when a channel list is not specified). For scanning measurements using the multiplexer modules, an error is generated if the internal DMM is disabled (see INSTrument:DMM[:STATe] command) or not installed in the mainframe. The internal DMM is not required for operations on the digital modules.   

• You can store at least 500,000 readings in memory and all readings are automatically time stamped. If memory overflows, the new readings will overwrite the first (oldest) readings stored; the most recent readings are always preserved. In addition, bit 12 is set in the Questionable Data Register's condition register (see Status System Introduction).

• The output from this command is affected by the settings of the FORMat:READing commands. Depending on the formats selected, each reading may or may not be stored with measurement units, time stamp, channel number, and alarm status information.

• The instrument clears all readings from memory when a new scan is initiated, when any measurement parameters are changed (CONFigure and SENSe commands), and when the triggering configuration is changed (TRIGger commands).  

• The instrument clears all readings from memory after a Factory Reset (*RST command), after an Instrument Preset (SYSTem:PRESet command), or when mainframe power is cycled.

Return Format

The command returns a series of readings in Definite-Length Block format. The syntax is a pound sign (#) followed by a non-zero digit representing the number of digits in the decimal integer to follow. This digit is followed by a decimal integer indicating the number of 8-bit data bytes to follow. This is followed by a block of data containing the specified number of bytes.

For example:

Example

This command reads the two oldest readings and erases them from memory.  

R? 2

Typical Response:  #231+2.87536000E-04,+3.18131400E-03

See Also

DATA:REMove?