Figure 1: software diagram

Both BLUE and RED sides are mostly identical. We will explain one side here, and all of it will apply to the other side, except  where explicitly stated otherwise.  All the software described here runs on the acquisition host, unless stated otherwise.

Server

As explained in the general introduction, the software consists of two ArcVIEW servers (one per side) that can run synchronized or independently.
There is a software module that controls the detector controller (Detector Head Electronics, or DHE), sending commands and receiving responses and data (an SDSU module for the BLUE side, and an EDTP11W module for the RED side). The data being read also gets sent to a Real Time Display module that sends the data to an external display program (ximtool, SAO or DS9).

Temperature control is different on each side. The RED side only allows reading the CCD temperature, and this is done through the FHH detector controller, which means that for this side the "temperature module" is the DHE module itself.
The BLUE side has a Lakeshore temperature module that controls/reads the Lakeshore temperature controller. This module allows adjustment of the CCD temperature setpoint, filters readings, generates asynchronous alarms, etc.

There is also a module that is connected to the Telescope Control System (TCS) of the 200 inch telescope through a network socket. This module reads status info from the TCS (RA, DEC, HA, UTC, etc) for inclusion in the image headers. Although this module allows full control of the TCS (telescope motion, focus, etc), the only operations currently being commanded from here are turning the flatfield calibration lamps on and off.

There is a separate program called the Serial Monitor, which listens through the serial port of the PC. When the aperture or red or blue camera filter changes, a message is received through the serial line from the instrument microcontroller. The Serial Monitor reads the message and reports the change through two networks ports, one for blue side changes and one for red changes. Each ArcVIEW server has a module that connects to the corresponding port, and in this way filter/aperture changes are reported back through the server to the client (GUI) and stored for insertion in the image headers.

Using information from the DHE module, the TCS, the temperatures, the aperture/filter info, and any "custom header" stored in a file template, the FITS module on the ArcVIEW server writes a fits format image with full header information.

Directory path and status information for any new fits image written to disk gets stored in an internal ArcVIEW database. This database module on the ArcVIEW server has its own network port; using this port another machine (the reduction host) can run a program called an "image puller" to get the needed information to transfer the fits image from the acquisition machine using SFTP protocol.


Clients

The ArcVIEW servers have network ports that accept client connections in order to send commands and/or receive asynchronous messages. All the commands that ArcVIEW accepts are ascii.

A client can connect in "full-connection mode" or in "blocking mode."
A fully-connected client will connect to a command port, and also to an asynchronous message port. In this way it will be able to send commands and receive immediate responses, asynchronous messages, and callbacks.
A blocking client will connect to a single port and send commands in a "blocking" state, which means that it will send the command but will not get any response until the command is done, even when the command takes a long time to execute (the EXPOSE command, for example).