... | ... | @@ -72,8 +72,7 @@ introduced into the system and observed on the two trigger unit outputs, located |
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This may be due to incorrect timings and delays having been set, or are the default when initialising
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the card.
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The aim of this section is to define a procedure that allows calibration of these delays so they may
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be avoided. The following functional overview highlights the different clock domains and their
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The aim of this section is to define a procedure that allows calibration of these delays so they may be avoided. The following functional overview highlights the different clock domains and their
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interfaces. Blue, denotes a WR clock domain, red denotes RF clocks and signals and orange/yellow
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indicate the VTU clock, a divided (by 8) version of the RF clock.
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... | ... | @@ -130,11 +129,9 @@ If the delayed version of NCO reset is clear of the RF stabilities we can procee |
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As the RF-NCO is reset only with frames, it is not possible to use `wr2rf nco-reset`.
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But it is possible to generate rffame every .5sec using the command:
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```
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./wr2rf -s $slot calib-vtu 1`
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./wr2rf -s $slot calib-vtu 1
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```
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## Methods – Steps 2, 3 and 4 - overview
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We plan to increase the programmable delays in each of the three places where metastability can
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... | ... | @@ -148,12 +145,12 @@ For steps 2-4, route the signal nco_reset to the front panel: |
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```
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./wr2rf -s $slot lemo-dbg-sel tmgio3 nco_reset
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```
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(Note: TBC but the rf1_nco_reset_cdelayed should be ok)
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## Method – Step 2 – fine delay
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Observe the skew between nco_reset and the T1 trigger unit output. Sweep across the full range of
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fine delay values 0 through to 15. This should be sufficient to observe two or three changes in the
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RF clocks sampling points. Choose a fine delay value mid-way between these sampling changes.
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fine delay values 0 through to 15. This should be sufficient to observe two or three changes in the RF clocks sampling points. Choose a fine delay value mid-way between these sampling changes.
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```
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./wr2rf -s $slot nco-reset-delay 1 75 [0-15]
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```
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... | ... | @@ -174,19 +171,18 @@ Binary chop through this delay space until the RF sampling point changes. A sequ |
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something like this for trigger unit 1 on RF channel 1:
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```
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./wr2rf -s $slot vtu 1.1 vtu-iodelay half_cycle_delay odelay_value
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./wr2rf -s $slot vtu 1.1 vtu-iodelay 0 0x0
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./wr2rf -s $slot vtu 1.1 vtu-iodelay 1 0x1f
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./wr2rf -s $slot vtu 1.1 vtu-iodelay 1 0x0
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./wr2rf -s $slot vtu 1.1 vtu-iodelay 1 0x10
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./wr2rf -s $slot vtu-odelay 1.1 half_cycle_delay odelay_value
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./wr2rf -s $slot vtu-odelay 1.1 0 0x0
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./wr2rf -s $slot vtu-odelay 1.1 1 0x1f
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./wr2rf -s $slot vtu-odelay 1.1 1 0x0
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./wr2rf -s $slot vtu-odelay 1.1 1 0x10
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```
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and so on, depending on where the RF sampling point changes.
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There is a small chance that the metastability region cannot be found. In this event, set the delay to
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midpoint of the search, e.g.
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There is a small chance that the metastability region cannot be found. In this event, set the delay to midpoint of the search, e.g.
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```
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./wr2rf -s $slot vtu 1.1 vtu-iodelay 0 0x1f
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./wr2rf -s $slot vtu-odelay 1.1 0 0x1f
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```
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## Method – Step 4 – T2 flip-flop
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... | ... | |