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Design Languages >> Verilog-AMS >> help with syntax
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Message started by manikandan on Feb 16^th, 2010, 12:52pm

Title: help with syntax
Post by manikandan on Feb 16^th, 2010, 12:52pm

hi
how can this logic be implemented in verilog A..

if(voltage input high )

condition 1

elseif(voltage input low)

condition 2

Title: Re: help with syntax
Post by Geoffrey_Coram on Feb 16^th, 2010, 2:46pm

module mymod(in);
input in;
electrical in;

parameter real vhigh = 0.7;
parameter real vlow = 0.3;

analog begin
if (V(in) > vhigh)
statement1;
else if (V(in) < vlow)
statement2;
end
endmodule

Title: Re: help with syntax
Post by manikandan on Feb 17^th, 2010, 2:00am

i got this error..pls help me fix it..according to voltage in i want the division ratio to change..

`include "constants.vams"
`include "disciplines.vams"

module freqdividerduty(out, vcoin, in);

output out; voltage out; // output
input vcoin; voltage vcoin; // input (edge triggered)
input in; voltage in;

parameter real vh=+3.3; // output voltage in high state
parameter real vl=0; // output voltage in low state
parameter real vth=(vh+vl)/2; // threshold voltage at input
parameter integer ratioone=40 from [40:inf); // divide ratio
parameter integer ratiotwo=41 from [40:inf); // divide ratio
parameter real tt=1n from (0:inf); // transition time of output signal
parameter real td=0 from [0:inf); // average delay from input to output

integer count,x,y;

analog begin
@(cross(V(vcoin) - vth, +1)) begin
count = count + 1; // count input transitions
if (count >= y)
count = 0;

end
if (count <= (y/2)) begin
x = 1;
end
else begin
x = 0;
end
end

if (V(in) = vh)
y = ratioone;
elseif (V(in) = vl)
y = ratiotwo;
else
y = 0;

V(out) <+ transition(x ? vh : vl, td, tt);

end

endmodule

"/proj/ek/vlsi4/common_libs/project_main_shared/freqdividerduty/veriloga/veriloga.va",
line 22: Warning: (Archaic Syntax) Does not comply with the Accellera
Verilog-AMS 2.0 Standard and beyond. To comply with the current
standard, assign a value to `y'. A variable that is never assigned a
value is considered a digital variable in Verilog-AMS and is therefore
not pure Verilog-A.
Error found by spectre during SpectreHDL compile.
"/proj/ek/vlsi4/common_libs/project_main_shared/freqdividerduty/veriloga/veriloga.va",
line 39: "if<<--? (V(in) = vh)"
"/proj/ek/vlsi4/common_libs/project_main_shared/freqdividerduty/veriloga/veriloga.va",
line 39: Error: syntax error
Maximum allowable errors exceeded. Exiting AHDL compilation....

Title: Re: help with syntax
Post by Andrew Beckett on Feb 17^th, 2010, 3:02am

If you actually indented your code (consistently), it would make it much easier for you to identify the mistake which is causing this (and then uncover the subsequent errors).

First thing, look around the line where the problem occurs:

Code:

x = 0;
end
end

if (V(in) = vh)

You have two successive end statements. The second of these is closing the begin associated with the analog statement. So it shouldn't be there.

Having fixed that, you have some other issues

Code:

if (V(in) = vth)

You've used an assignment rather than an equality check (==) in this statement. That said, using an equality check is not a good idea, because you would be attempting to compare a solved floating point number with a floating point constant. You should never do equality checks on floating point numbers (in pretty much any language) and even more so when one of them is numerically solved. You should check within a tolerance. I would suggest either doing:

Code:

if (abs(V(in)-vh)<1e-3)

i.e. give a tolerance on the comparison. Or maybe even:

Code:

if (V(in) >= vh)
y = ratioone;
else if (V(in) <= vl)
y = ratiotwo;
else
y = 0;

Note also that I changed the elseif to else if because that's also incorrect.

I didn't check the correctness of the model itself. Looks simple enough.

Regards,

Andrew.