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8842A
Instruction Manual
3-30
IFC Interface Clear -- A uniline message which clears only the interface (not the
8842A) by placing it in a known quiescent state.
REN Remote Enable -- A uniline message which, when received with MLA, switches
the 8842A to remote. When REN is set false, the 8842A switches to local and
removes local lockout.
DCL Device Clear -- A multiline message which is loaded into the input buffer as a
special device-clear command. DCL performs the same operation as the device-
dependent command *, except that it is read before any other characters that are
already present in the input buffer, and clears the entire input buffer. Processing
then continues normally. The action of DCL is not immediate; if the 8842A is
taking a reading when DCL is received, the DCL command is executed after the
measurement is finished.
LLO Local Lockout -- A multiline message which disables the front panel LOCAL
button. The result is that the local mode is not accessible by front panel control.
SPD Serial Poll Disable -- A multiline message which removes the serial poll enable
state.
SPE Serial Poll Enable -- A multiline message which causes the serial poll data (rather
than output buffer data) to be transferred on the bus once ATN becomes false.
3-55. Addressed Commands
Addressed commands are multiline messages which are accepted and interpreted by only
those devices currently addressed to listen. The 8842A responds to the following
addressed commands:
GET Group Execute Trigger -- (Not to be confused with the device-dependent Get
commands.) GET loads a trigger command into the input buffer and also
terminates the string at that point. Only a single character is loaded into the input
buffer. The trigger command is executed in its proper turn in the input string,
rather than immediately. When executed, GET initiates a measurement.
GTL Go To Local -- Causes the 8842A to switch to local. This command does not
enter the input buffer. If the display has been blanked (with a D1 command),
issue a D0 command before sending GTL.
SDC Selected Device Clear -- Identical to the universal command DCL, but is
accepted and interpreted by current listeners only. Therefore, it clears the 8842A
only if it is addressed to listen.
3-56. TALK-ONLY MODE
The talk-only mode lets you take advantage of the remote capability of the 8842A
without having to use an instrument controller. To put the 8842A in the talk-only mode:
1. Turn the 8842A POWER switch OFF.
2. Set the rear panel TALK ONLY bit switch to 1 (the up position).
3. Connect the 8842A via the IEEE-488 bus to your printer, data logger, or other device.
4. Configure the other device as a listener only.
5. Turn the 8842A POWER switch ON.