异步跨时钟域转换

Asynchronous Clock Conversion

两种情形：
Situation 1:主时钟频率245.76MHz，脉冲A由主时钟产生。采样时钟为122.88MHz，需要在采样时钟下正确采集脉冲A。
采用打两拍传递的方法进行采样。

Situation 2:主时钟频率122.88MHz，脉冲A由主时钟产生。采样时钟为245.76MHz，需要在采样时钟下正确采集脉冲A。
通过采集脉冲沿的方法来进行采样。

代码块：

'timescale 1ns/1ps

module ACC_mode1(
clka,clkb,rst,pulse_a,pulse_b,Sig
	);
	
input clka,clkb;
input rst;
input pulse_a;

output reg pulse_b;

reg [1:0] Sig;

always@(posedge clka) begin
	if(rst)
		Sig <= 0;
	else if(pulse_a == 1) 
		Sig <= 1;
	else if(pulse_b == 1)
		Sig <= 0;
	else
		Sig <= Sig;
end

always@(posedge clkb) begin
	if(Sig)
		pulse_b <= 1;
	else
		pulse_b <= 0;
end

endmodule

TestBench：

module TB_ACC_mode1;

reg	clka,clkb;
reg rst;
reg pulse_a;
wire pulse_b;
reg Sig;
reg [1:0] cnt;
wire pulse_cnt;

initial begin
	clka = 1;
	clkb = 1;
	rst = 1;
	cnt = 0;

	#4.069;
	rst = 0;

	#4.069;
	cnt = 1;
	#4.069;
	cnt = 0;
end

always begin
	#2.048 clka = ~clka;
end
always begin
	#4.069 clkb = ~clkb;
end

always@(posedge clka) begin
	if(rst)
		pulse_a <= 0;
	else if(cnt == 1)
		pulse_a <= 1;
	else
		pulse_a <= 0;
end

assign pulse_cnt = pulse_a;

ACC_mode1 u1(
XXXXXXXX
);

endmodule

预期波形：

'timescale 1ns/1ps


module ACC_mode2(
clka,clkb,rst,pulse_a,pulse_b,delay
	);

input clka,clkb;
input rst;
input pulse_a;
output pulse_b;

reg [2:0] delay;
reg [2:0] Sig;

always@(posedge clka) begin
	if(rst)
		delay <= 3'b000;
	else
		delay <= {
    
    delay[1:0],pulse_a};
end

always@(posedge clkb) begin
	if(rst)
		Sig <= 0;
	else
		Sig <= = {
    
    ~delay[2]} && delay[1];
end

assign pulse_b = Sig; 

endmodule

TestBench:

module TB_ACC_mode2;

reg	clka,clkb;
reg rst;
reg pulse_a;
wire pulse_b;
reg [1:0] cnt;

initial begin
	clka = 1;
	clkb = 1;
	rst = 1;
	cnt = 0;
	#8.138;
	rst = 0;

	#8.138;
	cnt = 1;
	
	#8.138;
	cnt = 0;
end

always begin
	#4.069 clka = ~clka;
end
always begin
	#2.048 clkb = ~clkb;
end

always@(posedge clka) begin
	if(rst)
		pulse_a <= 0;
	else if(cnt == 1)
		pulse_a <= 1;
	else
		pulse_a <= 0;
end

/*ACC_mode2 u2(
clka,clkb,rst,pulse_a,pulse_b,delay
	);*/

endmodule

预期波形：