Manual - 8500A Series Peak Power Meter - Giga-tronics

Series 8500A Peak Power Meters
3.2.4 Remote and Local Lockout Functions
The PPM accepts commands or output data only through the bus when it is in the Remote state. It is
placed in the Remote state by listen-addressing the instrument with REN asserted, per the IEEE-488 1978
standard. The PPM will ignore talk-addressing when it is not in the Remote state. Any Group Execute
Trigger (GET) command or any data sent to the instrument when it is addressed while not in Remote will
result in an error condition, and a service request will be generated if SRQ is enabled.
When in the Remote state, the front panel keys will not be active except for an escape sequence to return
to local control. The escape sequence is initiated by pressing [MENU]. At that time the PPM will suspend
all operations, including IEEE Bus interaction. The measurement being displayed on the front panel will
be replaced with a prompt to press F1 to return to local control, or F2 to abort the local escape sequence.
The instrument will not respond to any other keystrokes. If F1 is pressed, the instrument will return to
local control and resume normal manual operation. If F2 is pressed, the instrument will resume normal
operations in the Remote state as though no action had occurred. Once the unit has been returned to
Local control, it will return to Remote control the next time it is Listen-Addressed (LADS) with REN
asserted.
Another method to return to Local is achieved by sending a GTL (Go To Local) command from the GPIB
controller. The PPM will return to the Local control state when it receives this command, and can then be
returned to the Remote state the next time it is listen-addressed with REN asserted.
Besides the return to local escape sequence and the GTL universal command, the PPM will also exit the
Remote state when the REN line goes low.
After the PPM has entered the Remote state, a Local Lockout command can be sent to disable the use of
the front panel. This feature is intended to prevent accidental changes in front panel settings or
interruption of the program.
When the instrument is in the Local Lockout mode, the Return to Local escape sequence activated by the
MENU key is disabled. There is no way to regain control from the front panel once Local Lockout has
been commanded.
To go to the Local Lockout mode, the Local Lockout (LLO) bus command must be sent to the PPM. The
LLO light on the PPM’s front panel will not be turned on at that time, but the instrument will be in the
LLO state. At the next change in the state of the instrument, either a change in the addressed state of the
PPM on the GPIB or any keystroke made on the front panel, the LLO light will turn on. If a front panel
keystroke is made, it is ignored and will not affect the state of the instrument. Subsequent attempts to
control the unit from the front panel will also be ignored.
3.2.5 Output Modes
The PPM outputs data over the GPIB in the following six output modes:
• Update Trigger Reset
• Update Data Continuously
• Plot
• Temperature Difference
• Status Byte
• Stand Alone Plot
The PPM can be in only one output mode when it is talk-addressed. For example, the unit cannot be
programmed to plot and then immediately output the difference in temperature since the last calibration.
If the PPM receives more than one output mode instruction, the most recent command will supersede all
previous output commands.
3-4 Manual No. 20790, Rev C, November 1998
Superceded by Revision D, March 2009