MODULE trcstp
   !!======================================================================
   !!                       ***  MODULE trcstp  ***
   !! TOP :   time stepping of TOP models (passive tracers)
   !!======================================================================
   !! History :   1.0  !  2004-03 (C. Ethe) Original code
   !!----------------------------------------------------------------------
#if defined key_passivetrc
   !!----------------------------------------------------------------------
   !!   'key_passivetrc'                                         TOP models
   !!----------------------------------------------------------------------
   !!   trc_stp       : passive tracer system time-stepping
   !!----------------------------------------------------------------------
   USE oce_trc        ! ocean dynamics and active tracers variables
   USE trc            ! ocean passive tracers variables 
   USE trctrp         ! passive tracers transport
   USE trcsms         ! passive tracers sources and sinks
   USE prtctl_trc     ! Print control for debbuging
   USE trcdia         ! passive tracer diagnostics
   USE trcdit         ! ???
   USE trcrst         ! ???

   IMPLICIT NONE
   PRIVATE

   PUBLIC   trc_stp   ! called in step.F90 module

   !!----------------------------------------------------------------------
   !! NEMO/TOP 1.0 , LOCEAN-IPSL (2005) 
   !! $Id$ 
   !! Software governed by the CeCILL licence (modipsl/doc/NEMO_CeCILL.txt)
   !!----------------------------------------------------------------------

CONTAINS

   SUBROUTINE trc_stp( kt, kindic )
      !!----------------------------------------------------------------------
      !!                     ***  ROUTINE trc_stp  ***
      !!                      
      !! ** Purpose :   Time loop of TOP passive tracer
      !! 
      !! ** Method  :   Compute the passive tracers trends 
      !!                Update the passive tracers
      !!----------------------------------------------------------------------
      INTEGER, INTENT( in ) ::   kt       ! ocean time-step index
      INTEGER, INTENT( in ) ::   kindic   ! ???
      CHARACTER (len=25) :: charout
      !!----------------------------------------------------------------------

      IF( MOD( kt, ndttrc ) /= 0 )   RETURN            ! routine called only every ndttrc time step

      IF(ln_ctl) THEN
         WRITE(charout,FMT="('kt =', I4,'  d/m/y =',I2,I2,I4)") kt, nday, nmonth, nyear
         CALL prt_ctl_trc_info(charout)
      ENDIF

                       CALL trc_rst_opn( kt )          ! Open tracer restart file 

                       CALL trc_sms( kt )              ! sink and source of passive tracers

                       CALL trc_trp( kt )              ! transport of passive tracers

      IF( lrst_trc )   CALL trc_rst_wri( kt )          ! write tracer restart file

                       CALL trc_dia( kt, kindic )      ! diagnostics
      !
   END SUBROUTINE trc_stp

#else
   !!----------------------------------------------------------------------
   !!   Dummy module                                          No TOP models
   !!----------------------------------------------------------------------
CONTAINS
   SUBROUTINE trc_stp( kt )        ! Empty routine
      INTEGER, INTENT(in) :: kt
      WRITE(*,*) 'trc_stp: You should not have seen this print! error?', kt
   END SUBROUTINE trc_stp
#endif

   !!======================================================================
END MODULE trcstp