Question about particular HDL code

• Jul 10, 2006

• #1

R

rickyice

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if(a>5)
b=1;
else
b=0;


now, if (input)a=x,and then b=???

 

• Jul 10, 2006

• #2

the_risk_master

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Re: hdl questions

it depends on the value of x, it is stated in your code that a must satisfy greater than 5 for b=1.

 

• Jul 10, 2006

• #3

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polukir

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hdl questions

Here, b will get "0" as the if condition fails here. Generally in the case of failing "if" .... else will get executed."else" doesn't look for any condition..failing of "if" is enough for "else" to get the execution.

 

• Jul 10, 2006

• #4

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rickyice

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Re: hdl questions

polukir is right,
thank you

 

• Jul 11, 2006

• #5

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spauls

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Re: hdl questions

Why dont you simulate and check in waveform.

 

• Jul 11, 2006

• #6

J

jjww110

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hdl questions

i think it depend on simulation tools

 

• Jul 11, 2006

• #7

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rickyice

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Re: hdl questions

i did it

 

• Jul 16, 2006

• #8

M

mvkarthik

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Re: hdl questions

If this is for a non-synthesizable code, then it's going to have a value of 0. but if this is a synthesizable code then after synthesis it's still 'X'.

 

• Jul 19, 2006

• #9

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stevepre

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Re: hdl questions

it's definitely 0

 

• Jul 19, 2006

• #10

neo_chip

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Re: hdl questions

hi,

f(a>5)
b=1;
else
b=0;

Click to expand...

if a is greater than 5, b wiil be equal to 1...................
if a is less than or equal to 5 or others(like x,z...), b will be equal to zero

 

• Sep 25, 2006

• #11

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praveen_venigalla

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Re: hdl questions

It is not a matter of synthesis or simulation.....

In Synthesis it will take a MUX and a comparator....so it will show X if u simulate synthesized netlist with
input 'X'.

But in rtl code it should give output '0'.

Praveen.

 

• Apr 11, 2007

• #12

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r63511

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hdl questions

stevepre is correct. Put it in another way: if you're answering your final test, write down 'b = 1' if you're facing real problem in your design, particularly for PL simulation, you will get 'x'.

 

• Apr 12, 2007

• #13

U

uditkumar1983

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hdl questions

Hi,
it's definitely 0 because if statement will see only condition is satisfied or not , and X will be treated as condition is not satisfied so b will be always 0.

 

• Apr 12, 2007

• #14

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sumit_techkgp

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hdl questions

The RTL code will give 0 output
Sumit

 

• Apr 12, 2007

• #15

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alisha

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Re: hdl questions

yups it wil b zero!!