The Free On-line Dictionary of Computing (30 December 2018):

Active Reconfiguring Message

    (ARM) An efficient mechanism which allows
   reconfiguration of the hardware logic of a system according to
   the particular data received or transmitted.

   In ARM each message contains extra information in a
   Reconfiguring Header in addition to the data to be
   transferred.  Upon arrival of the message the Reconfiguring
   Header is extracted, decoded and used to perform on-the-fly
   hardware reconfiguration.  As soon as the hardware has been
   reconfigured the data information of the message can be
   processed.

   [In what contect is this term used?]

   (1997-06-06)