RE: [oc] "case" synthsis and netlist simulation

["Illan Glasner" <iglasner@zumanetworks.com>]

   Hi,

	the don't care etc are handle depend on the synthesis tool usualy base on either really don;t care or ignore and by this I mean that let say you write 

2'b 1_don;t_care than in really don;t care it can come as either 2'b10 or 2'b11 while in ignore the synthesis will trunc it to 1'b1 and ignore the "lsb".

as for priority/parallel case etc you can give again depend on the synthesis tool attribute/pragma/constarain etc to do what you want.

however if what you want is priority why don;t you simple use if else which by defenition give you the priority you want.

for example instead of :

> casez(REQUEST)
> 3'b1??: GRANT = 3'b100;
> 3'b01?: GRANT = 3'b010;
> 3'b001: GRANT = 3'b001;

write something like

     if (req[2]) ...
else if (req[1]) ...
else if (req[0]) ...
else ...

as for what to look if your tool show you the "gates" that priority is a chain of and's however if it use LUT or ATOM than it might be harder to see.

what you can simple do is run simulation and see if it give priority or not.

have a nice day

   Illan


-----Original Message-----
From: jae lim [mailto:jlim0011@yahoo.com]
Sent: Monday, July 15, 2002 8:41 AM
To: cores@opencores.org
Subject: [oc] "case" synthsis and netlist simulation



> 
> Hello everyone,
> 
> I am just trying to see how the synthesis
> tool(design
> compiler ) will implment the following "case":
> ************************************************
> module case_try(GRANT,REQUEST);
> 
> input [3:1] REQUEST;
> output [3:1] GRANT;
> 
> reg  [3:1] GRANT;
> always @(REQUEST)
> casez(REQUEST)
> 3'b1??: GRANT = 3'b100;
> 3'b01?: GRANT = 3'b010;
> 3'b001: GRANT = 3'b001;
> 
> default: GRANT = 3'b000;
> 
> endcase
> endmodule
> 
> ******************************************
> after synthsis, how can I tell if it is implemented
> as
> priorized one or MUX? and what is supposed to be?
> 
> Now I have the netlist of the module based on
> "class.db" library from synopsys. How can I test it
> with my simulation level testbench? suppose the
> class.db library is in the
> /home/hwang/synopsys/libaries/class.db, should I
> just
> put:
> 
> `include "/home/hwang/synopsys/libaries/class.db"
> 
> into my testbench(which also includes the netlist
> file)? and if this is the case, how can I write the
> sdf annoate? 
> 
> I am pretty new in this area, thank you for your
> paticience...
> 
> Have a nice day!
> 
> Jay
> 
> 
> 
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