Subject: Re: VHDL extensions and styles pertinent to Verilog + Re: HDL Con Paper
From: VhdlCohen@aol.com
Date: Wed Dec 12 2001 - 14:30:53 PST
By the way, Synplify also synthesizes that code. Attached is a PDF of the
code and result. And that brings an interesting question: Do we want to
include the support of Implicit FSMs style with mutiple clocks? I read
Cliff's answer, and he has good points, but the tools seem to support this
style. In other words, if vendors support the multiple clocks in a block, do
we really want to say "NO, we won't let you do that". I thought our job is
not necessarily to teach good style, but rather define templates and
attributes for use in interroperability. From our spec "1.1 Scope
This standard defines a set of modeling rules for writing Verilog HDL
descriptions". These are not guidelines on how to do design.
Comments?
Ben Cohen
n a message dated 12/12/01 12:43:15 PM Pacific Standard Time,
eagle64@email.msn.com writes:
> Xilinx ISE reports an error - that the behavior contains a timing control
> and an embedded event control. Adding the wrapper, as shown below, leads
> to a synthesiazable model of the implicit state machine, but it vaporizes
> unless the pors are added. withthe ports added the tool will build a
> controlling state machine with wait states.
>
> Mike Ciletti
>
> module n (q, d, clk);
> output q;
> input d, clk;
> //wire clk, d; // redundant
> reg q;
> always begin:wrapper
>
> @(posedge clk) begin
> q <= 0;
> @(posedge clk) q <= 1;
> @(posedge clk) q <= d;
> end
> end // wrapper
> endmodule
>
>
>
----------------------------------------------------------------------------
Ben Cohen Publisher, Trainer, Consultant (310) 721-4830
<A HREF="http://www.vhdlcohen.com/">http://www.vhdlcohen.com/> vhdlcohen@aol.com
Author of following textbooks:
* Real Chip Design and Verification Using Verilog and VHDL, 2002 isbn
0-9705394-2-8
* Component Design by Example ", 2001 isbn 0-9705394-0-1
* VHDL Coding Styles and Methodologies, 2nd Edition, 1999 isbn 0-7923-8474-1
* VHDL Answers to Frequently Asked Questions, 2nd Edition, isbn 0-7923-8115
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