How to Configure the Correlator

The correlator should automatically configure when you go to a new SCHED file with a different correlator configuration. Occasionally CACOR fails to configure the requested configuration. If this is the case it will show you on the right side of CACOR which blocks have failed, necessitating re-programming the correlator.

Alternatively, if you don't have you have left your correlator configuration file as ``NULL'' in your SCHED file then you can select the config file from with CACOR, and then ask it to re-program the correlator for that configuration.

The Correlator Configuration Book in the Control Room lists and describes most of the available correlator configurations.

However, the PSR configurations may not be accurate as other ones. A list of available correlator configurations appears in a box in the upper right corner of the CACOR window.

If you have set you config as ``NULL'' in SCHED, choose set the correlator configuration in CACOR as follows:

First, stop the scan and close your current data file:
CAOBS$>$ stop
CAOBS$>$ corr closefile

In the correlator configuration field in the top right side of the CACOR window click and select the configuration you want.

To re-program the correlator:
Press the button in CACOR.

A window pops up showing very quickly the programming operation. When completed (after approximately 1 second) it will disappear if successful, and you should see your requested correlator config file in the upper right field of the CACOR window.
CHECK the config file field in the top right corner is that which you requested. If specified in your SCHED file the config file should correspond to the bandpasses displayed in the upper part of the CAOBS window.

If configuring the correlator failed, the pop-up programming window will stay, in which case attempt to reprogram the failed blocks by again pressing the config button.
Press the button.

If after several tries it is still unsuccessful, you will need to manually reset the blocks Note: after resetting the correlator block manually, go back to the Control Room and configure the correlator again.

After apparently successful configuration of the correlator:
CHECK by viewing the correlation function (or lag spectrum) using SPD to be sure the correlator is generating fringes. Slew to a calibrator then on SPD:

First select the visibilities you wish to display. For example:

$>$ select aa,bb

To show XX and YY on Freq 1 for all baselines.

Then plot the lag spectrum:
$>$ l
You should see a sinc function displaying a single bright peak. See these examples for bright and weak calibrators . If the lag spectrum is not generating sensible fringes you should re-program the correlator.

After correlator configuration the bottom panel of the CACOR display show the integration time and some other monitor information. This panel is used by the system to display configuration information and error messages. The state field near the top of the page indicates whether a scan is in progress (either GO or STOPPED). The file field indicates whether a RPFITS data file is open.

During a scan the second section of the CACOR gui will display a set of lines for every cycle which will look something like:

NEWCYC: REFBM=0 OBSTYP=0x0 FQIds=1,1 SRCId=1
DELBAT:  01:05:10.000: 0:  -7992  -4984 * -4932 -6504 -23744 || -7992
OLDCYC:  01:05:00.000    NA=5 NF=2 ON SRC 11111

DELBAT displays the delays in nanoseconds from each antenna - in this example antenna 3 is the reference antenna. The last DELBAT field is the offset between CACCC and XBONES in nanoseconds. This number should be 7500$\pm$1500 for observations using a 10s integration time (12500$\pm$1500 for 15s).