HP 54645A User's And Service Manual page 275

Messages
Delay time =
When the Horizontal Mode is Delayed, this message appears while you are
adjusting the Delay knob, to inform you of the current delay time setting.
Digital channels are not available in XY or Roll mode
When setting the Horizontal Mode to XY or Roll, you cannot select digital
channels D0-D15 on HP 54645D.
Digital channels cannot be moved in XY or Roll mode
When setting the Horizontal Mode to XY or Roll, you cannot change the
position of channels D0-D15 on HP 54645D.
Display and setup are saved to memory
This message appears when you save the current display and setup using the
Trace memory menu.
Duration time is at limit
This message appears when, in the Advanced Trigger menu, you try to adjust
the duration setting for a pattern to a value less than the minimum or greater
than the maximum. The minimum and maximum values are determined by
the Time/Div and sampling interval, so you may be able to work around the
problem by changing the Time/Div setting. See Chapter 4, "MegaZoom
Concepts and Oscilloscope Operation," for more information on the interaction
between various oscilloscope time base functions.
Illegal Instruction
A processing fault occurred during operation. Cycle power to the
oscilloscope, or perform a hard reset by cycling power with the two rightmost
softkeys depressed. If this does not correct the problem, contact your HP
Sales Office for assistance.
Key not used in this menu
This message appears when you press a softkey that is not valid for the
current menu.
Measurement already active
This message appears when you press the Measure key for a measurement
that is already defined and is being updated in the message line.
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