PC Connection

The ethernet link to the PC is controlled from the PC Connection menu (Figure 4.3), activated by the button of the same name in the upper left corner of the SCACQ window. The Establish Connection button makes the ethernet connection to PSYS. PSYS must be in listen mode for the connection to be established.

To break the connection (at the end of the night), click on the Close Connection button in this menu, and answer yes to the prompt menu that appears. You can also press the Status button to display the current status of the network connection.

If the connection needs to be broken, then re-established, you may get a Syserr response and an error message in the console window when you press the connect button, indicating that the address that ezra is attempting to use is already in use by the PC. Just press the Establish Connection button again and the system will try to connect using a different address.

The Interrupt and Reboot buttons provide special interrupt-level communications with the PC. Because of their drastic effects, they are placed in the PC Connection menu to avoid accidently tripping them. Both controls ask for verification before proceeding.

• Interrupt sends a command to the PC to stop a scan which is in progress. The scan is stopped at the end of the next even beam. The data in the FITS file up to this point will be good, but the FITS header will indicate the wrong number of bands which may cause a problem with some FITS reading programs.

• Reboot sends an interrupt signal to reboot the PC. As our system has gotten more reliable, we have used this command less and less. However, it is very powerful: when normal network communications do not seem to be working at all, or when the PC is stuck in some very confused state, it is usually possible to reboot the PC with this switch, as long as the cabling is correct and the hardware is OK. Use only as a last resort!