(* Defination of state space matrix  *)
   A = {{-833.3 ,-25.18} , {5193 ,-7.145}}   ;
   B = { {303.03},{0}}  ;
   c={{ 0 , 60/(2*[Pi])  }};
   d= {{0}} ;

(* Response to 12 volt supply ( Analog ) *)
   ssmC= StateSpaceModel[{A, B, c, d } ]
   Res=OutputResponse[ssmC , 12 , t ]   ;
   PlotA=Plot[ {Res}, {t,0, 15 },PlotLabel-> {" step Response "}, PlotRange-> 1500]



(* Response to 12 volt supply (ZOh) *)

   DssmZoH= ToDiscreteTimeModel [ssmC , 0.020 ,Method -> "ZeroOrderHold"]

   Res  = OutputResponse[DssmZoH ,12*UnitStep[n], n ]

   PlotB= DiscretePlot[{ Res },{n,0,80} , PlotLegends -> {"ZoH " }, PlotRange-> 1500]

(* Response to 12 volt supply (FD) *)
   add= {{1,0} , {0,1}} + 0.0020*A
   ddd= 0.0020*B
   ssmC=StateSpaceModel[{add, ddd , c, d },SamplingPeriod->0.0020 ]
   Res6=OutputResponse[ssmC ,12*UnitStep[n], n ] ;
   PlotC= DiscretePlot[{ Res6 },{n,0,40} , PlotLegends -> {"Forword diff" }, PlotRange-> 1500]