HDLbits---Circuits---Sequential Logic---Finite State Machines第四部分

1.Exams/ece241 2013 q8

bash 复制代码
module top_module (
    input clk,
    input aresetn,    // Asynchronous active-low reset
    input x,
    output z ); 
parameter start=2'b0,
    one=2'b01,
    two=2'b10,
    three=2'b11;
    reg[1:0] state,next_state;
    always@(posedge clk or negedge aresetn) begin
        if(aresetn==0)
            state<=start;
        else
            state<=next_state;
    end
    always@(*) begin
        case(state)
            start: 
                begin
                    if(x)
                        next_state<=one;
                    else
                        next_state<=start;
                end
             one: 
                begin
                    if(x)
                        next_state<=one;
                    else
                        next_state<=two;
                end
             two: 
                begin
                    if(x)
                        next_state<=three;
                    else
                        next_state<=start;
                end
             three: 
                begin
                    if(x)
                        next_state<=one;
                    else
                        next_state<=two;
                end
            default:
                begin
                    next_state<=start;
                end
            
        endcase
    end
    assign z=(next_state==three);
    
            
endmodule

2.Exams/ece241 2014 q5a

bash 复制代码
module top_module (
    input       clk,
    input       areset,
    input       x,
    output      z
); 
 
parameter  MSB    =  3'b001;
parameter  OUT_1  =  3'b010;
parameter  OUT_0  =  3'b100;
 
reg  [2:0]     state;
reg  [2:0]     next_state;
always @(posedge clk or posedge areset) begin
    if (areset) begin
        state <= MSB;
    end
    else begin
        state <= next_state;
    end
end
always @(*) begin
    next_state = state;
    case(state)
        MSB: begin
            if (x) begin
                next_state = OUT_1;
            end
            else begin
                next_state = MSB;
            end
        end
        OUT_1: begin
            if (x) begin
                next_state = OUT_0;
            end
            else begin
                next_state = OUT_1;
            end
        end
        OUT_0: begin
            if (~x) begin
                next_state = OUT_1;
            end
            else begin
                next_state = OUT_0;
            end
        end
        default: begin
            next_state = MSB;
        end
    endcase
end
assign z = (state==OUT_1);
 
endmodule

3.Exams/ece241 2014 q5b

bash 复制代码
module top_module (
    input clk,
    input areset,
    input x,
    output z
); 
reg state,next_state;
    parameter A=0,B=1;
    always@(posedge clk or posedge areset) begin
        if(areset)
            state<=A;
        else
            state<=next_state;
    end
    always@(*) begin
        case(state)
            A:
                begin
                    if(x==0)
                        next_state<=A;
                    else
                        next_state<=B;
                end
            B:
                begin
                        next_state<=B;
                end
            default:
                next_state<=A;
        endcase
    end
    assign z=(((state==A)&&x==1)||(state==B)&&(x==0));
                        
endmodule

4.Exams/2014 q3fsm

bash 复制代码
module top_module (
    input       clk,
    input       reset,   // Synchronous reset
    input       s,
    input       w,
    output      z
);
 
parameter  IDLE =  5'b00001;
parameter  A    =  5'b00010;
parameter  B    =  5'b00100;
parameter  C    =  5'b01000;
parameter  D    =  5'b10000;
reg  [4:0]    state;
reg  [4:0]    next_state;
reg  [10:0]   cnt;
always @(posedge clk) begin
    if (reset) begin
        state <= IDLE;
    end
    else begin
        state <= next_state;
    end
end
always @(*) begin
    case(state)
        IDLE: begin
            if (s) begin
                next_state = A;
            end
            else begin
                next_state = IDLE;
            end
        end
        A: begin
            next_state = B;
        end
        B: begin
            next_state = C;
        end
        C: begin
            next_state = D;
        end
        D: begin
            next_state = B;
        end
        default: begin
            next_state = IDLE;
        end
    endcase
end
always @(posedge clk) begin
    if (reset) begin
        cnt <= 'd0;
    end
    else begin
        case(next_state)
            IDLE: begin
                cnt <= 'd0;
            end
            A: begin
                cnt <= 'd0;
            end
            B: begin
                if (w) begin
                    cnt <= 'd1;
                end
                else begin
                    cnt <= 'd0;
                end
            end
            C: begin
                if (w) begin
                    cnt <= cnt + 'd1;
                end
                else begin
                    cnt <= cnt;
                end
            end
            D: begin
                if (w) begin
                    cnt <= cnt + 'd1;
                end
                else begin
                    cnt <= cnt;
                end
            end
        endcase
    end
end
 
assign z = (state==D && cnt=='d2);
endmodule

5.exams/2014_q3bfsm

bash 复制代码
module top_module (
input      clk,
input      reset,   // Synchronous reset
input      x,
output     z
);
parameter  A  =  3'b000;
parameter  B  =  3'b001;
parameter  C  =  3'b010;
parameter  D  =  3'b011;
parameter  E  =  3'b100;
reg  [2:0]  state;
reg  [2:0]  next_state;
always @(posedge clk) begin
if (reset) begin
state <= A;
end
else begin
state <= next_state;
end
end
always @(*) begin
next_state = state;
case(state)
A: begin
if (x) begin
next_state = B;
end
else begin
next_state = A;
end
end
B: begin
if (x) begin
next_state = E;
end
else begin
next_state = B;
end
end
C: begin
if (x) begin
next_state = B;
end
else begin
next_state = C;
end
end
D: begin
if (x) begin
next_state = C;
end
else begin
next_state = B;
end
end
E: begin
if (x) begin
next_state = E;
end
else begin
next_state = D;
end
end
default: begin
next_state = A;
end
endcase
end
assign z = (state==D) || (state==E);
endmodule

6.Exams/2014 q3c

bash 复制代码
module top_module (
input        clk,
input [2:0]  y,
input        x,
output       Y0,
output       z
);
parameter  A  =  3'b000;
parameter  B  =  3'b001;
parameter  C  =  3'b010;
parameter  D  =  3'b011;
parameter  E  =  3'b100;
reg  [2:0]   state;
always @(*) begin
case(y)
A: begin
if (x) begin
state = B;
end
else begin
state = A;
end
end
B: begin
if (x) begin
state = E;
end
else begin
state = B;
end
end
C: begin
if (x) begin
state = B;
end
else begin
state = C;
end
end
D: begin
if (x) begin
state = C;
end
else begin
state = B;
end
end
E: begin
if (x) begin
state = E;
end
else begin
state = D;
end
end
default: begin
state = A;
end
endcase
end
assign Y0 = state[0];
assign z = (y==D) || (y==E);
endmodule

7.Exams/m2014 q6b

bash 复制代码
module top_module (
input  [3:1]   y,
input          w,
output         Y2
);
parameter   A  =  3'b000;
parameter   B  =  3'b001;
parameter   C  =  3'b010;
parameter   D  =  3'b011;
parameter   E  =  3'b100;
parameter   F  =  3'b101;
reg  [3:1]   next_state;
always @(*) begin
case(y[3:1])
A: begin
if (w) begin
next_state = A;
end
else begin
next_state = B;
end
end
B: begin
if (w) begin
next_state = D;
end
else begin
next_state = C;
end
end
C: begin
if (w) begin
next_state = D;
end
else begin
next_state = E;
end
end
D: begin
if (w) begin
next_state = A;
end
else begin
next_state = F;
end
end
E: begin
if (w) begin
next_state = D;
end
else begin
next_state = E;
end
end
F: begin
if (w) begin
next_state = D;
end
else begin
next_state = C;
end
end
default: begin
next_state = A;
end
endcase
end
assign Y2 = next_state[2];
endmodule

8.m2014 q6c

bash 复制代码
module top_module (
input  [6:1]    y,
input           w,
output          Y2,
output          Y4
);
assign Y2 = ~w & y[1];
assign Y4 = (w&y[2]) | (w&y[3]) | (w&y[5]) | (w&y[6]);
endmodule

9.Exams/m2014 q6

bash 复制代码
module top_module (
input clk,
input reset,     // synchronous reset
input w,
output z);
parameter A=0,B=1,C=2,D=3,E=4,F=5;
reg[2:0] state,next_state;
always@(posedge clk) begin
if(reset)
state<=A;
else
state<=next_state;
end
always@(*) begin
case(state)
A:
begin
if(w)
next_state<=A;
else
next_state<=B;
end
B:
begin
if(w)
next_state<=D;
else
next_state<=C;
end
C:
begin
if(w)
next_state<=D;
else
next_state<=E;
end
D:
begin
if(w)
next_state<=A;
else
next_state<=F;
end
E:
begin
if(w)
next_state<=D;
else
next_state<=E;
end
F:
begin
if(w)
next_state<=D;
else
next_state<=C;
end
default:
next_state<=A;
endcase
end
assign z=((state==E)||(state==F));
endmodule

10.Exams/2012 q2fsm

bash 复制代码
module top_module (
input clk,
input reset,     // synchronous reset
input w,
output z);
parameter A=0,B=1,C=2,D=3,E=4,F=5;
reg[2:0] state,next_state;
always@(posedge clk) begin
if(reset)
state<=A;
else
state<=next_state;
end
always@(*) begin
case(state)
A:
begin
if(w)
next_state<=B;
else
next_state<=A;
end
B:
begin
if(w)
next_state<=C;
else
next_state<=D;
end
C:
begin
if(w)
next_state<=E;
else
next_state<=D;
end
D:
begin
if(w)
next_state<=F;
else
next_state<=A;
end
E:
begin
if(w)
next_state<=E;
else
next_state<=D;
end
F:
begin
if(w)
next_state<=C;
else
next_state<=D;
end
default:
next_state<=A;
endcase
end
assign z=((state==E)||(state==F));
endmodule

11.Exams/2012 q2b

bash 复制代码
module top_module (
    input [5:0] y,
    input w,
    output Y1,
    output Y3
);
    parameter A = 3'b000,B = 3'b001,C = 3'b010,D = 3'b011,E = 3'b100,F = 3'b101;
    assign Y1 = w&y[A];
    assign Y3 = ~w&(y[B]|y[C]|y[E]|y[F]);
endmodule

12.Exams/2013 q2afsm

bash 复制代码
module top_module (
    input clk,
    input resetn,    // active-low synchronous reset
    input [3:1] r,   // request
    output [3:1] g   // grant
); 
parameter A=0,B=1,C=2,D=3;
    reg[1:0] state,next_state;
    wire r1,r2,r3;
    assign r1=r[1],r2=r[2],r3=r[3];
    always@(posedge clk) begin
        if(resetn==0)
            state<=A;
        else
            state<=next_state;
    end
    always@(*) begin
        case(state)
            A: 
                begin
                if(r1==1)
                    next_state<=B;
                    else if(r2)
                    next_state<=C;
                    else if(r3)
                        next_state<=D;
                         else
                             next_state<=A;
            end
             B: 
                begin
                if(r1==1)
                    next_state<=B;
                else 
                    next_state<=A;
            end
             C: 
                begin
                    if(r2==1)
                    next_state<=C;
                else 
                    next_state<=A;
            end
             D: 
                begin
                    if(r3==1)
                    next_state<=D;
                else 
                    next_state<=A;
            end
        endcase
    end
    assign g[3]=(state==D);
    assign g[2]=(state==C);
    assign g[1]=(state==B);
    
                    
            
endmodule

13.exams/2013_q2bfsm

bash 复制代码
module top_module (
    input         clk,
    input         resetn,    // active-low synchronous reset
    input         x,
    input         y,
    output        f,
    output        g
);  
parameter   START  =  9'b000000001;
parameter   OUT_F  =  9'b000000010;
parameter   X_1    =  9'b000000100;
parameter   X_2    =  9'b000001000;
parameter   X_3    =  9'b000010000;
parameter   OUT_G  =  9'b000100000;
parameter   G_1    =  9'b001000000;
parameter   WAIT   =  9'b010000000;
parameter   G_0    =  9'b100000000;
reg  [8:0]   state;
reg  [8:0]   next_state;
always @(posedge clk) begin
    if (!resetn) begin
        state <= START;
    end
    else begin
        state <= next_state;
    end
end
always @(*) begin
    next_state = state;
    case(state)
        START: begin
            next_state = OUT_F;
        end
        OUT_F: begin
            next_state = X_1;
        end
        X_1: begin
            if (x) begin
                next_state = X_2;
            end
            else begin
                next_state = X_1;
            end
        end
        X_2: begin
            if (x) begin
                next_state = X_2;
            end
            else begin
                next_state = X_3;
            end
        end
        X_3: begin
            if (x) begin
                next_state = OUT_G;
            end
            else begin
                next_state = X_1;
            end
        end
        OUT_G: begin
            if (y) begin
                next_state = G_1;
            end
            else begin
                next_state = WAIT;
            end
        end
        WAIT: begin
            if (y) begin
                next_state = G_1;
            end
            else begin
                next_state = G_0;
            end
        end
        G_1: begin
            next_state = G_1;
        end
        G_0: begin
            next_state = G_0;
        end
        default: begin
            next_state = START;
        end
    endcase
end
assign f = state==OUT_F;
assign g = (state==OUT_G) | (state==G_1) | (state==WAIT);
endmodule
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