[widar-wg] Blanking at subarray changes

[Brent Carlson]

The mechanism for blanking at the LTA is already in place.  It can be 
done by disabling correlation in the correlator chip, or in the LTA, by 
blocking frames coming from the correlator chip.  The former will result 
in the first output frame having an accumulator overflow condition, but 
the latter would not have such a problem as the correlator chip would 
still be humming along and dumping frames, which the LTA just throws away.

A simpler (well, set 1 bit instead of 16) way yet is in the LTA, turn 
off the "Enable Data Flow", which will cause the LTA to stop sending out 
frames, and ignore frames coming from the correlator chip.  When data 
flow is enabled again, the first frame coming out will be labelled as an 
overrun frame, not bad in itself, just indicating that the correlator 
chip was discarding frames because its output frame buffer was full.

So, take your pick.  I think the 2nd way is the cleanest all around.

Brent

On 10/06/2011 10:30 AM, Michael Rupen wrote:
> In testing Martin's new subarray code this morning we noticed that
> the output frame rate from the BlBs goes to 0 whenever a subarray
> correlator configuration is changed.  This means that one loses data
> for ALL subarrays, whenever any subarray has a configuration change (e.g.,
> when you first start up a new subarray).
>
> The root of this is that blanking is currently done on the GigE chip,
> which affects the entire BlB.  (This should mean that BlBs which are not
> used by the changing subarray aren't affected, but we have not checked that
> directly yet.)
>
> Would it be possible to blank at the LTA instead of at the GigE chip?
> or otherwise implement different blanking per CC?
>
>          -- Michael
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-- 
Brent R. Carlson
Brent.Carlson at nrc-cnrc.gc.ca
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