/*******************************************************************************
  procedure: begwrk
  purpose:   issue command to controller
  synopsis:  int CALLTYPE begwrk( fun, rd, rs )
  input:     fun = code of command to issue:
               1 = count impulses during exposure time
               2 = count time when number of impulses is set
               3 = intensimeter
               5 = stop controller
             int rd = data port address, (data register)
             int rs = control port address, that identifies controller (state
                 register)
  result:    0 = operation successful
             -1 = communication error
             -2 = controller can't make this function to present time or error
                  code function
             -3 = parameter error (unknown command)
*******************************************************************************/

#ifdef DEBUG
int retspot_beg;
#endif // def DEBUG

int CALLTYPE begwrk( fun, rd, rs )
  int fun, rs, rd;
{

  register int i, j;
  /* buffer of receive/transmit message */
  unsigned char bufmsg[LNGMSG];

#ifdef DEBUG
  retspot_set = retspot_beg = retspot_get = retspot_init = retspot_tr =
      retspot_rc = retspot_out = retspot_in = 0;
#endif // def DEBUG

  /* do nothing, if using FakeDevice */
  if (FakeDevice)
    return 0;

  /* depending on the command to issue... (function code filter) */
  switch (fun)
  {

    /* count impulses during exposure time */
    case 1:

    /* count time when number of impulses is set */
    case 2:

    /* intensimeter */
    case 3:

    /* stop controller */
    case 5:

      /* transmit message NCYCL cycles or until return value is 0 */
      for ( i = 0; i < NCYCL; i++ )
      {
        j = tr_message( fun, rd, rs, bufmsg, 0 );

        if (j == 0)
          break;

        if (j == -2)
          {

#ifdef DEBUG
            retspot_beg = 1;
#endif // def DEBUG

            return -2;
          }
      }

      /* if unknown return code */
      if (j != 0)
      {

#ifdef DEBUG
        retspot_beg = 2;
#endif // def DEBUG

        /* return error code */
        return -1;
      }

#ifdef DEBUG
      retspot_beg = 0;
#endif // def DEBUG

      /* exit positively */
      return 0;

    /* unknown command */
    default :

#ifdef DEBUG
      retspot_beg = 3;
#endif // def DEBUG

      /* return error code */
      return -3;

  }
}