SystemVerilog 编写FSM
---- # SystemVerilog 编写FSM ----
好书：
https://github.com/yllinux/blogPic/blob/master/doc/CummingsSNUG2003SJ_SystemVerilogFSM.pdf
https://github.com/yllinux/blogPic/blob/master/doc/CummingsSNUG2019SV_FSM1.pdf
题目
SystemVerilog实现
module ExampleFSM (
input logic clk ,
input logic reset ,
input logic X ,
output logic Y
);
typedef enum logic [2:0] {A, B, C, D, E} state ; // 定义枚举类型
state currentState, nextState ; // 声明自定义类型变量
always_ff @(posedge clk , posedge reset) // 状态转移，同步时序，推荐3行式
if (reset) currentState <= A ;
else currentState <= nextState ;
always_comb begin // 状态转移条件判断，组合逻辑
nextState = 3'bxxx ; //@ loopback，需要写上
case (currentState)
A : if (X) nextState = C ;
else nextState = B ;
B : if (X) nextState = D ;
else nextState = B ; //@LB
C : if (X) nextState = C ;
else nextState = E ;
D : if (X) nextState = C ;
else nextState = E ;
E : if (X) nextState = D ;
else nextState = B ;
default : nextState = A ; // 需要写上
endcase
end
// assign Y = (currentState == D | currentState == E) ; // 组合输出
// always_ff @(posedge clk , posedge reset)
// if (reset)
// Y <= 1'b0 ;
// else begin
// Y <= (nextState == D | nextState == E) ;
// end
always_ff @(posedge clk , posedge reset)
if (reset)
Y <= 1'b0 ;
else begin
Y <= 1'b0 ;
case (nextState)
D : Y <= 1'b1 ;
E : Y <= 1'b1 ;
// don't need default
endcase
end
endmodule
仿真
`timescale 1ns/1ns
module ExampleFSM_TB ();
logic clk=1 ;
logic reset ;
logic in ;
logic out ;
logic expectOut ;
logic [31:0] i ;
ExampleFSM dut (
.clk ( clk ),
.reset ( reset ),
.X ( in ),
.Y ( out )
);
logic [2:0] testVector [1000:0] ;
initial begin
$readmemb ("TestBenchVector.txt", testVector, 0, 19) ;
i = 0;
reset = 1; in = 0;
#200ns; $finish;
end
always @(posedge clk) begin
{reset, in, expectOut} <= #2 testVector[i] ;
$display(reset, in, expectOut, $time);
end
always @(negedge clk) begin
if (expectOut !== out) begin
$display("wrong output for inputs %b, %b != %b, address %d", {reset, in}, expectOut, out, i, $time);
end
i = i + 1 ;
end
always begin
clk <= 1; #5 ;
clk <= 0; #5 ;
end
//-----------------------------------------
// for VCS generate fsdb file
//-----------------------------------------
initial begin
$fsdbDumpfile("./digital.fsdb");
$fsdbDumpvars(0,ExampleFSM_TB,"+all");
$fsdbDumpflush();
end
endmodule
激励向量文件：TestBenchVector.txt
10_0
10_0
10_0
00_0
01_0
01_1
01_0
00_0
01_0 // 01_1
00_1
10_1
11_0
11_0
11_0
11_0
11_0
11_0
11_0
11_0
11_0
