Q3a: FSM

https://hdlbits.01xz.net/wiki/Exams/2014_q3fsm

module?top_module?(

????input?clk,

????input?reset,???//?Synchronous?reset

????input?s,

????input?w,

????output?z

);

????localparam?

????????A????=?3'd0,

????????B???=??3'd1,?

????????C???=??3'd2,

????????D???=??3'd3,

????????E???=??3'd4;

????reg?[2:0]?state,?next_state;

????reg?[2:0]?W_VA;

????

???always?@?(*)

????????case?(state)

????????????A:?next_state?=?s?B:A;

????????????B:?next_state?=?C;

????????????C:?next_state?=?D;

????????????D:?next_state?=?E;

????????????E:?next_state?=?C;

????????????default?next_state?=?A;

????????endcase

????always?@?(posedge?clk)

????????if?(reset)

????????????state?<=?A;

????????else

????????????state?<=?next_state;

????always?@?(posedge?clk)

????????case?(next_state)

????????????C:W_VA?<=?{2'b00,w}?;

????????????D:W_VA?<=?{W_VA[2],w,W_VA[0]};

????????????E:W_VA?<=?{w,W_VA[1:0]};

????????????default?W_VA?<=?3'b000;

????????endcase

????assign?z?=??next_state?==?C?&&?((W_VA==3'b011)??||?(W_VA==3'b101)?||?(W_VA==3'b110));?????

endmodule