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Train / Burst Sync

Macro: BurstSync

This button allows you to set the trace to sync on the start of the train or burst interval. This will almost always be what you want to do when Burst is active.

However, this Sync setting is only effective if Trigger is active and Gen Sync is selected in the Trigger dialog. When the Gen Sync button has been activated there, it changes to show the current Sync source. In this case, it will show the channel and stream plus 'Train' or 'Burst'.

This 'internal' sync is a powerful advantage of having Daqarta generate bursts as well as view them; if generated by an external source, you would have to use Normal trigger mode and carefullly set Holdoff to get the display to trigger on the start of each burst, not on some arbitrary cycle of the waveform within the burst. (Without Holdoff, any one of the cycles in a burst could be an acceptable trigger.)

Note that even with Train/Burst Sync active, the waveform in the burst region will not appear stationary unless you have Reset Phase on Train or Reset Phase on Burst active in the main Freq dialog. That forces the software oscillator to restart at the Phase setting at the start of each burst; otherwise, the main wave just continues to run unseen between bursts, and the next burst starts at whatever phase the main wave has at that instant. In that case the burst envelope position will be stationary, but the wave will appear to be rolling through it. This is equivalent to a real hardware oscillator whose output is passed through an unsynchronized envelope generator or tone switch.

Different options are offered depending upon the nature of the burst train. If Train Cycle is set to Count times Burst Cycle (the default condition), the resultant burst train may appear to be the same regardless of the Count of bursts in that train. However, suppose in the Freq dialog you select Reset Phase On Train, but not on Burst. Each train will always have the same phase at the start, but successive bursts in the train may have different starting phases as the generator continues to run freely between train starts. In this case the trace will appear unchanging if you toggle Train Sync on, but if you toggle the button again to Burst Sync, the display will change as the starting phase of each burst in the train differs.

If you set Train Cycle to a larger value than Count times Burst Cycle (by setting Trace Cycle after Burst Cycle), then you will only be allowed Train Sync, not Burst Sync.

The total size of the Train Cycle, not counting Train Lag, must be 4294967295 samples or less... about 24.8 hours at a 48000 Hz sample rate. That total includes the product of Train Count times Burst Cycle. If you try to enter any value that would bring the total over the limit, that entry will be constrained such that the limit is met.

Burst Timing Modulation Sync

When Train Cycle timing is modulated, the Sync button will be disabled. It will also be disabled if Burst Cycle is modulated and Count is set to 1. In either of these cases you can usually get an equivalent result with Trigger Mode set to Normal instead of Gen Sync. Set Trigger Holdoff to the product of the base Burst Cycle times Count, and Trigger Source to the proper output channel. Then adjust Trigger Level to trigger on the first rising edge of a burst. You will need Reset Phase on Burst (and possibly Reset Phase on Train) so that the burst looks the same for each trigger.

With this method, the trigger point will be delayed by the time needed for the Burst Rise phase to reach the trigger level. If this is a problem, just set Trigger Delay to the desired negative value to see the earlier part of the burst.

In special cases where you need each burst to start on a random phase, you may still use the above Normal trigger method if you only need output from one channel. Just set the other channel to create the identical burst modulation, only set the main Tone Frequency to 0 and Phase to 90 degrees. Each "burst" will become a positive pulse that is easy to trigger on. You can typically set Rise and Fall to zero and include those amounts in High, which will insure that the trigger comes at the very start of the burst. Make sure to set Trigger Source to this "dummy" channel, and set the output Volume to a very low level (or to Off) to insure against leakage into the active channel. Note that although you may want to view the dummy channel while setting up the trigger, you don't need to display it after that... the real channel should show what you want.

Macro Notes:

L.1.BurstSync=1 or L.1.BurstSync="T" sets Left Stream 1 Train Sync. 2 or "B" sets Burst Sync, and 0 toggles the sync off. Note that quotes are required around "T" and "B"

If Burst Sync is not available (see above), attempting to set it (via "B" or 2 will set Train Sync.

If the specified Stream is off, or Burst is off, then the Train / Burst Sync button is disabled. Attempting to use BurstSync will result in an error message stating "Control disabled. Aborting macro."

Note that there is a single global Sync source, not separate sources for each channel or stream. The channel and stream prefixes select which stream will be chosen as the Sync source. When BurstSync goes from on to off, the global sync reverts to the Left Stream 0 Tone Frequency until you set it to something else.

Note: If a BurstSync command is given when the Burst Dialog is open for any channel or stream, and the control is disabled in that dialog, then the macro will abort with an error message... regardless of which channel or stream is the target of the command. You can however, safely test BurstSync with an IF statement.

SyncMode is a read-only variable that returns the current sync mode. See the full description in the Tone Sync Macro Notes section.

See also Burst Overview, Burst Dialog Controls


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