String Length Selection
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5.9 String Length Selection
The digital multimeter can send different length messages to the computer whereby
the desired message length is selected with L0 or L1. The latest measurement reading
is returned if the computer sends the command L0. The status information is not
output in response to L0. In response to L1 the instrument sends the most recent data
including the status information.
5.10 SRQ Mode
If the digital multimeter is not to be continually interrogated by the computer but
instead the digital multimeter is to request service from the computer when a status
change has taken place, SRQ mode (service request) must be switched on with the
command Q1.
A SRQ is sent, for example, when keyboard input has been made, when error
messages appear. Utilization of SRQ mode requires that the connected computer can
recognize a SRQ and reply to it with a serial poll (see computer manual).
5.11 Operation of the Digital Multimeter as TALKER
On request by the computer, the instrument sends a message containing its present
status and the most recent measurement reading. For this purpose the computer must
address the instrument as TALKER. The instructions how to do this are contained in
the manual of the computer manufacturer. The message ‘ADR’ is lit in the right
window of the display when the instrument has been addressed as TALKER.
The transmitted message consists of a character string and a fixed terminator at the
end of each character string enabling the computer to recognize the end of the
transmission. The message consists of two message units. The first unit contains the
data of the most recent measurement reading or calculation result, and the second unit
contains data concerning the programing status. The two message units are
transmitted as complete data record. The string terminator is fixed and defined with
IEEE-488.2 standard as "LF + EOI".
The ASCII (ISO 7 bit) code is used for the transmission.
The length of the second message unit is fixed and always consists of 27 characters
plus the terminator character. The length of the first message unit is 14 characters for
output of measurement readings and calculation results.
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