The Arcon NEXUS TRAM must orchestrate complicated activities with other TRAMS in response to user requests. The simplest requests are changes of state and the generation of reports; the most complicated is an observation.
For this, the Nexus must request telescope and motor movements and get the resulting status, set up parameters for taking a CCD exposure, and terminate any idling or residual activity from a previous observation. It must then request that the COMMNODE TRAM read data from the CCD, that the SEQUENCER TRAM output the waveforms needed to read data out of the CCD, and that its own program buffer pixels as they come from the CommNode and get them back to the reduction computer. It also sends a copy of the image data to the DISPLAYNODE TRAM, so that the data may be displayed in real-time.
The Nexus is typically controlled by commands sent down through the user interface. These may either be the direct result of actions taken by the user or commands read from a disk file (called a "macro" or "script").
The user interface sends its commands through the muxnex daemon, a program residing on the host system connected to the transputer systems through a Transtech BBKS4 interface board, and on to the Nexus either directly or via the optional MAGIC MEMORY TRAM.