## Synchronisation

Flags are used for inter-process synchronisation, or to request some specific actions.

- ASTRO (Astronomical Computation requested) (CLEARED)
  This flag is set by OBS when changing source. It is expected and cleared by ASTRJ when relevant computations have been done.
- TCPIP (Dialog with antenna micros) (CLEARED)
  This flag is set by FLAG1S every second. It is expected and cleared by INTERP, which reads information from the antenna micros on such occasions.
- TRACK Tracking (SET)
  This flag indicate the Antennas and subreflectors are in position and tracking. It is set and cleared by INTERP. It is expected by CORREL to start data acquisition.
- UT (UT time change) (CLEARED)
  This flag indicate the UT time has changed. It is set by FLAG1S and expected and cleared by CORREL.
- COR (CORrelator acquisition required) (CLEARED)
  This flag is set by OBS when an acquisition is requested. It is expected and cleared by CORREL.
- SUP (Interferometer setup done) (CLEARED)
  This flag is set by task CORREL whenever the parameters of an acquisition are ready. It is expected and cleared by RDI.
- DAT (Interferometer data ready) (CLEARED)
  This flag is set by task CORREL_SPECTRA whenever new data is available from the correlators. It is expected and cleared by RDI.
- SPECTRE (Correlator data ready) (CLEARED)
  This flag is set by CORREL when an acquisition finished. It is expected and cleared by CORREL_SPECTRA which reads the data from the correlators and set flags DAT when done.
- ALARM (Alarm) (CLEARED)
  This flag may be set by some program. It signals a problem...
- STARTED (Acquisition started) (CLEARED)
  This flag is set by CORREL when the acquisition is running. It is expected and cleared by RDI.
- RED (RDI ready) (SET)
  This flag is set by RDI when it is ready. It is expected (and later cleared) by OBS.
- CONTROLC (`^C` pressed) (CLEARED)
  Set when `^C` is pressed in OBS.