Previous: Starting up the system
Up: Using the DAS
Next: Setting the image format
Previous Page: Starting up the system
Next Page: Setting the image format
DAS commands are entered at the ICL prompt which may look like ICL> or may show the time of day: 01:33:22.4> . If you don't see one of these prompts (in particular, if you have the DCL prompt `$'), the system isn't ready for DAS commands.
Most commands take parameters for which you may give values on the command line e.g.
ICL> <command> <channel> <p1> <p2> <p3>If you leave out a parameter, the system will prompt you for its values. The parameters are parsed by relative position on the command line so you cannot leave out parameters from the middle of the command.
Most prompts include a suggested value enclosed between slashes e.g.
READOUT_SPEED Read-out speed of CCD /'QUICK'/ >If you press return at this point, the system uses the suggested value.
If you are prompted for a parameter value and don't understand what is needed, you can enter a question mark and press return. The system sends you a brief sentence of explanation and repeats the prompt.
If you want to escape from a prompt sequence, enter two exclamation marks and press return. The system will abandon the command with no effect on the hardware.
The commands and parameters are not case sensitive, except for titles of observations and commentary, where mixed case is preserved in the observing log and FITS headers.
Most ICL commands to the DAS operate on one detector channel and are queued by the system until the channel is ready to receive the command. The queueing feature allows you to enter several DAS commands and to regain control of the ICL terminal as soon as the commands have been accepted; the commands execute `in the background'. For example, if you type
ICL> run red 1800 "NGC1068" ICL> bin red 4 4 ICL> run red 30 "NGC1068"the system will execute, on the red channel, an 1800-second exposure, a binning operation and a 30-second exposure. The binning will not take effect until the first exposure has finished and the second exposure will not start until the binning has been set. Control of ICL will be returned to you as soon as the system accepts the 30-second exposure, which should be within a few seconds of you typing that command. You are then free to send commands to other parts of the observing system.
You will be informed, by a message to the terminal, when each DAS command starts and finishes. The system may report that it is starting one command before another has finished. This is normal, and reflects the the system's knowledge of which low-level actions can safely be executed in parallel. Similarly, the system may hold over some part of a command after it reports that the command has finished; it does this when the next command can usefully overlap the last. This feature is included to decrease the `wasted' time between observations.
Some DAS commands are not queued, notably those that alter the course of the current exposure. These commands are marked as non-queuing in the command reference below.
The queuing feature only operates inside the DAS and only for individual detector channels: you cannot use queuing to synchronize two detector channels or to synchronize DAS commands with other commands.
If you change your mind about a command you have queued, use the abort command to delete it. Abort <channel> first deletes the command or commands that are currently executing. Abort <channel> all deletes all commands in the queue.