SIS 3320

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250 MHz 12-bit VME flash-ADC module SIS3320-250 from Struck Innovative Systems

At 250 MHz samples are taken every 4 ns. The module has eight input channels grouped in four 2-channel groups. The resolution of the samples is 12 bits over a range of 10 V. This corresponds to 2.5 mV signal resolution.

The firmware of the module in use (version SIS3320-250-M-2A02-1-v103) allows for a dedicated accumulator mode. For more information about the SIS3320-250 (including addressing and settings), refer to the User Manual.


The SIS3320 has a large number of options, and they are all very similar. You can do many things that are all almost the same, but different in some important details. Here are the definitions that are relevant to the Compton photon detector read-out.

  • Triggering: A trigger can be used to start the sampling or to stop the sampling. The trigger can be generated from the external front panel lemo connector, or through an internal VME key address write. A pre-/post-trigger value can be defined to delay the external start/stop or autostart/internal stop.
  • Memory page: Pages of 32MSamples / 4^n can be defined (up to 64 samples small). When pages are used, they are automatically in circular buffering. To do the same with single shot buffering, one has to use the "sample length stop" to limit the number of stored samples after a trigger is received. Upon reading the ADC memory over VME, pages up to 8Mb can be used.
  • Single shot buffering strategy: the trigger defines the start of writing samples to the buffer until the buffer (or page) is full or a predefined memory depth has been reached.
  • Circular buffering strategy: Every sample is written to the circular buffer (or page) and the trigger defines the stop. The stop pointer is also the start of the event and stored in the event directory. A bit in the event directory indicates whether a full wrap-around was completed before the stop.
  • Single Event mode: The full memory of 32MSamples is used as a big circular buffer or as single shot memory.
  • Multi Event mode (ENABLE_MULTIEVENT): The memory is divided in pages or events for the acquisition of shorter signals. Up to 512 stop pointers for the individual pages are stored in the event directory. "Sampling logic armed" is cleared after last event.
  • Autostart mode (ENABLE_AUTOSTART): The ADC automatically advances to the next page in multi-event mode and starts sampling in the circular buffer. Sampling starts with the "Sampling logic arm" command, and in multi-event mode with the end of the event on the previous page.
  • Accumulators: Each of the 6 accumulators have a 24-bit counter and 36-bit sum (for definitions of when which accumulator is filled, see user manual). They are stored in the event directory and cleared at the beginning of every event. When accumulators are stored, only one event can be stored in the event directory in multi-event mode :-(

Modes of operation

These setup modes are accessible in the CRL through


where mode is the mode number.


Mode CRL Flags Description
1 Accumulator, Sampling


Long buffers, lemo start and stop


Short wrapped buffers, autostart, lemo stop
3 Multievent


Multievent, lemo start, stop at preset number of samples
4 Triggered


Multievent, lemo start, autostart, wrap around, no accumulator

Last update: wdconinc 18:29, 14 October 2009 (UTC)

Front panel

LED assignment LEMO control in/out
Left Description Right Description
A VME access SAM Sampling busy
P Power SRT Start
R Ready STP Stop
U User TRG Trigger
Ch IN (left) OUT (right)
4 Clock in Clock out
3 Start Ready for start (armed)
2 Stop Ready for stop (busy)
1 User in Trigger out