Subject: Initial Blocks fail with Synopsys Tools
From: Clifford E. Cummings (cliffc@sunburst-design.com)
Date: Fri Oct 05 2001 - 17:40:26 PDT
Hi, all -
I believe I tested this on Synopsys version 2000.08. I have been teaching
for years that initial blocks are not synthesizable. I tested them years
ago with Synopsys tools. I know of no version of the Synopsys tools that
ever ignored initial blocks. I still have some old Synopsys documentation.
If I get time I will verify that this was illegal with earlier versions of
Synopsys tools.
I was very surprised to learn that Synplicity ignored initial blocks. I
consider this to be a serious flaw in the Synplicity tools.
module dff (q, d, clk, rst_n);
output q;
input d, clk, rst_n;
reg q;
initial q <= 0;
always @(posedge clk or negedge rst_n)
if (!rst_n) q <= 1'b0;
else q <= d;
endmodule
//Error: /.../dff.v:6: INITIAL statements are not supported by synthesis.
Regards - Cliff
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