I just discovered https://bitbucket.org/tmidas/midas/issues/338/mfec-ro_stopped-is-now-forbidden

> Dear Midas experts,
> 
> I noticed that a check was added to mfe.cxx in 1961af0d6:
> 
> +      /* check for consistent common settings */
> +      if ((eq_info->read_on & RO_STOPPED) &&
> +          (eq_info->eq_type == EQ_POLLED ||
> +           eq_info->eq_type == EQ_INTERRUPT ||
> +           eq_info->eq_type == EQ_MULTITHREAD ||
> +           eq_info->eq_type == EQ_USER)) {
> +         cm_msg(MERROR, "register_equipment", "Events \"%s\" cannot be read when run is stopped (RO_STOPPED flag)", equipment[idx].name);
> +         return 0;
> +      }
> 
> This commit was by Stefan in May 2022.
> 
> A commit few days later, 28d9c96bd, removed the "return 0;", and updated the
> error message to:
> 
> "Equipment \"%s\" contains RO_STOPPED or RO_ALWAYS. This can lead to undesired side-effect and should be removed."
> 
> So such FEs can run but there is still an error at start up. The 
> documentation at https://daq00.triumf.ca/MidasWiki/index.php/ReadOn_Flags
> states with RO_STOPPED "Readout Occurs" "Before stopping run".
> Which seems to indicate that the removing the RO_STOPPED bit from a SC FE
> would just result in an additional read not happening just prior to a run
> stop. However reading scheduler() in mfe.cxx I see in the the main loop:
> 
>  if (run_state == STATE_STOPPED && (eq_info->read_on & RO_STOPPED) == 0) 
>     continue;
> 
> So it seems to me that the a EQ_PERIODIC equipment needs RO_STOPPED to be set
> otherwise it will not read out data while there is no DAQ run.
> 
> Can someone explain the purpose of this check and error message? Perhaps it
> was put in place with only DAQ FEs, not SC FEs in mind? And should the 
> documentation in the wiki actually be "s/Before stopping run/While run is stopped/"?
> 
> Thanks,
> 
> Nick.