FSMD application

Finite state machine with data path:

FSM used to change the state, tell the datapath when and how to do different calculations,  and datapath used to do different calculations.

Use FSMD to implement the function of c++ code which calculates the square root of a number:

while(sqaure<=data){  // control
square=sqaure+delta;  //calculate
delta=delta+2;
}
return delta/2 - 1  

Input of FSM:                 (square<=data), rst, clk

Output of FSM:               calculate, clean, returnnum(control signals) 

Input of DATA_PATH:     datain, calculate, clean, returnnum

Output of DATA_PATH:  dataout 

|FSM |<-------------------------(square<=data)------------------------- | DATA_PATH |--------> dataout

|FSM | ----------------calculate, clean, returnnum------------------>| DATA_PATH |<-------- datain

FSM: 

always@(posedge clk)begin
    if(rst) cstate<=idle;  //asynchronize rst
    cstate<=nstate;
end
always@(*)begin
    calculate=0; 
    return_num=0;
    clean=0; 
    nstate=cstate;
    case(cstate)
       idle: if(start) nstate=s1;
       s1: if(sqreg<=datain) calculate=1;
           else begin count=0; nstate=s2; end
       s2: begin returnnum=1; n_state=s3;end
       s3: begin n_state=s0; clean=1;end
    endcase
end

DATA_PATH:

    always@(posedge clk)begin
      if(!rst)begin dreg=0;sqreg=0;dout=0; end
      else if(calculate) begin sqreg = sqreg+dreg; dreg = dreg+2;end
      else if(returnnum) dout=(dreg>>1) -1;
      else if(clean)begin dreg=0;sqreg=0; end
    end