quartus sythesize question

Hi, FvM

First of all thanks for your reply, I'll give you an example to describe the problem I'm having.

You can see the Main_Seq module, PWRGD_a is the input, but I marked it as output. The final result b_EN will become high during simulation, which is also successful in quartus sythesize, but b_EN will not become high in the actual synthesis circuit.

Do you know how to verify this problem or use some settings in sythesize to avoid this problem?

module top(
output a_EN,
output b_EN,
input PWRGD_a,
input POWER,
input CLK_2M
);

// Rst Control
wire Rst;
assign Rst = POWER ? 1'b1 : 1'b0;

// sync signal
wire w_PWRGD_a;
sync sync_inst(
.clk(CLK_2M),
.Rst(Rst),
.iSync(PWRGD_a),
.oSync(w_PWRGD_a)
);

Main_Seq main_seq_inst(
.clk(CLK_2M),
.Rst(Rst),
.a_EN(a_EN),
.b_EN(b_EN),
.PWRGD_a(w_PWRGD_a)
);

endmodule

module sync(
input clk,
input Rst,
input iSync,
output oSync
);

reg rSync;
reg [10:0] iSync_delay;
assign oSync = rSync;

always @(posedge clk) begin
if(!Rst) begin
rSync <= 1'b0;
iSync_delay <= {11{1'b0}};
end
else begin
iSync_delay <= {iSync_delay[9:0], iSync};
end
end

always @(posedge clk)
begin
if(!Rst) begin
rSync <= 1'b0;
end
if(~|iSync_delay)
begin
rSync <= 1'b0;
end
if(&iSync_delay)
begin
rSync <= 1'b1;
end
end

endmodule

module Main_Seq(
input clk,
input Rst,
output a_EN,
output b_EN,
output PWRGD_a
);

reg a_EN_ff;
reg b_EN_ff;

assign a_EN = a_EN_ff;
assign b_EN = b_EN_ff;

always @(posedge clk) begin
if(!Rst) begin
a_EN_ff <= 0;
b_EN_ff <= 0;
end
else begin
a_EN_ff <= 1;
if(PWRGD_a) begin
b_EN_ff <= 1;
end
end
end

endmodule

`timescale 1ns/1ns

module tb_top;
reg clk;
parameter clk_period = 500;
initial begin
clk = 1'b0;
end

wire a_EN;
wire b_EN;
reg PWRGD_a;

always @(clk)
#(clk / 2.0) clk <= !clk;

reg POWER;

initial begin
POWER = 1'b0;
PWRGD_a = 1'b0;
#(1000000) // 1ms
POWER = 1'b1;
end

always @(posedge a_EN & POWER) begin
PWRGD_a <= 1'b1;
end

top top_inst(
.a_EN(a_EN),
.b_EN(b_EN),
.PWRGD_a(PWRGD_a),
.POWER(POWER),
.CLK_2M(clk)
);

endmodule

BR,

SamPF

Hi ShengN

First of all thanks for your reply

You are right because this is a real problem we have in real systems, when we simulate everything is correct and we load to FPGA it does not work, so the synthesized circuit is correct, but how do I get this in simulation The problem is what we care about, so hopefully you can tell me what I can do in the simulation to prevent this problem, thanks.

BR,

Sam