Status Reporting 7
Agilent InfiniiVision 5000 Series Oscilloscopes Programmer's Reference 517

Message Queue

The message queue contains the text of the last message written to the
advisory line on the screen of the oscilloscope. The length of the
oscilloscope's message queue is 1. Note that messages sent with the
:SYSTem:DSP command do not set the MSG status bit in the Status Byte
Register.