DC中关于 hign-fanout net的问题
时间:10-02
整理:3721RD
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代码如下:
module test(clk_800M,rst_n1,rst_n2,din,dout);
input clk_800M,rst_n1,rst_n2;
input[1023:0] din;
output[1023:0] dout;
reg[1023:0] dout;
wire rst_n;
assign rst_n=rst_n1&rst_n2;
always@(posedge clk_800M or negedge rst_n)
if(!rst_n)
dout<='d0;
else
dout<=din;
endmodule
DC综合之后的 check_design报告中有这么一句话:
Warning: Design 'test' contains 1 high-fanout nets. A fanout number of 1000 will be used for delay calculations involving these nets. (TIM-134)
Net 'clk_800M': 1024 load(s), 1 driver(s)
1
问两个问题啊
(1) 设计中应该有两条 high-fanout nets 才对啊 rst_n也是一条吧
(2) 报告中的那个 1 是什么意思 1条 high-fanout net ?
module test(clk_800M,rst_n1,rst_n2,din,dout);
input clk_800M,rst_n1,rst_n2;
input[1023:0] din;
output[1023:0] dout;
reg[1023:0] dout;
wire rst_n;
assign rst_n=rst_n1&rst_n2;
always@(posedge clk_800M or negedge rst_n)
if(!rst_n)
dout<='d0;
else
dout<=din;
endmodule
DC综合之后的 check_design报告中有这么一句话:
Warning: Design 'test' contains 1 high-fanout nets. A fanout number of 1000 will be used for delay calculations involving these nets. (TIM-134)
Net 'clk_800M': 1024 load(s), 1 driver(s)
1
问两个问题啊
(1) 设计中应该有两条 high-fanout nets 才对啊 rst_n也是一条吧
(2) 报告中的那个 1 是什么意思 1条 high-fanout net ?
报告中那个 1 不是 1条 high-fanout net的意思 将代码改成如下:
module test(clk_800M,rst_n,din,dout);
input clk_800M,rst_n;
input[1023:0] din;
output[1023:0] dout;
reg[1023:0] dout;
always@(posedge clk_800M or negedge rst_n)
if(!rst_n)
dout<='d0;
else
dout<=din;
endmodule
check_design中显示的信息如下:
Warning: Design 'test' contains 2 high-fanout nets. A fanout number of 1000 will be used for delay calculations involving these nets. (TIM-134)
Net 'clk_800M': 1024 load(s), 1 driver(s)
Net 'rst_n': 1024 load(s), 1 driver(s)
1
(1)为什么这样写就变成了两条了呢,难道第一种写法中 rst_n不是 high-fanout net吗