====== How to run combined S800 + GRETINA ======
In order to run the combined S800 + Gretina daq, the following steps need to be taken:
  - [[S800 DAQ tools#Running the S800 DAQ|Run the S800 ReadoutGUI]] for the S800 data acquisition system as you normally would on the S800 spdaqXX (note, at present X=50), and click the ''Start'' button.   
  - Make sure that the external synchronization and external clock are enabled in the S800 ULM trigger module. (Just click on the corresponding "check boxes" in the ULM GUI.)
  - Make sure that GRETINA DAQ is ready.
  - Using one of the dataU6 Linux boxes (e.g. u6pc2) Log in using the experimental account to **ddasdaq3** or any other of the systems dual homed to the GRETINA/NSCLDAQ network.
  - Use command ''godaq'' to run the Readout control program.
  - Click the ''Start'' button.  This will grab remote control over the S800 Readout GUI. The S800 daq will now be in slave mode.
  - You should now be able to start runs as needed in the experiment's ReadoutGUI running on the dual homed system.

You can check the ring buffers using the command **/usr/opt/nscldaq/xxxxx/bin/ringbuffer status**, where xxxxx is the nscldaq version. If everything has started correctly you should have the following ring buffers in the dual homed system (e.g. ddasdaq3):

  * **experimental-user-name (e.g. e14045)**: This ring is where sampled coincidence data is placed.  This is done via a tapcat, glom pipeline.
  * **spdaqXX.rawccusb**: It will provide raw data from the S800 CAMAC crate.
  * **spdaqXX.rawvmusb**: It will provide raw data from the S800 VME crate.
  * **spdaqXX.s800filter**: It will provide the event built, reformated data from the S800 Filter. During a run, data are pushed from this ring into the GRETINA GEB.

In addition to the normal **stagearea** structure in the experiment account, three directories are added that will be used to store raw S800 data:

  * **~/stagearea/rawccusb**: Event files containing raw CCUSB data from the S800.
  * **~/stagearea/rawvmusb**: Event files containing raw VMUSB data from the S800.
  * **~/stagearea/s800filter**: Event files containing event build, reformatted S800 data from the S800 Filter.