ElecDude

conditional operator (?:) vs IF statement

noreply@blogger.com (Anonymous) — Thu, 2 Nov 2017 01:30:00 +0530

Here is the simple code for comparing conditional operator and if statement.

Code:

module testing;

reg foo;

wire [3:0] c1,c2,c3;

reg [3:0] a=1,b=3,cif1,cif2,cif3;



assign c1 = foo ? a : b;

//equality
assign c2 = (foo==1) ? a : b;

//case equality
assign c3 = (foo===1) ? a : b;



always@(foo or a or b) begin

if (foo)

cif1 = a;

else

cif1 = b;

    //equality

if (foo==1)

cif2 = a;

else

cif2 = b;

    //case equality

if (foo===1)

cif3 = a;

else

cif3 = b;

end



initial begin

$monitor("@%3t :: foo=%b, a=%x, b=%x,   c1=%x, c2=%x, c3=%x,   cif1=%x ,cif2=%x ,cif3=%x", $realtime,foo,a,b,c1,c2,c3,cif1,cif2,cif3);

#10 foo=1;

#5 a=a+1;

#10 foo=0;

#5 b=b+1;

#10 foo=1;

end



endmodule

OUTPUT:

@  0 :: foo=x, a=1, b=3,   c1=X, c2=X, c3=3,   cif1=3 ,cif2=3 ,cif3=3  @ 10 :: foo=1, a=1, b=3,   c1=1, c2=1, c3=1,   cif1=1 ,cif2=1 ,cif3=1  @ 15 :: foo=1, a=2, b=3,   c1=2, c2=2, c3=2,   cif1=2 ,cif2=2 ,cif3=2  @ 25 :: foo=0, a=2, b=3,   c1=3, c2=3, c3=3,   cif1=3 ,cif2=3 ,cif3=3  @ 30 :: foo=0, a=2, b=4,   c1=4, c2=4, c3=4,   cif1=4 ,cif2=4 ,cif3=4  @ 40 :: foo=1, a=2, b=4,   c1=2, c2=2, c3=2,   cif1=2 ,cif2=2 ,cif3=2

Based on the simulation, when the condition is X conditional operator outputs X whereas if statement outputs else part. Except this, moreover no difference in execution of these two.

Hardware/Software cosimulation using Xilinx and Matlab

noreply@blogger.com (Innovative thinkers) — Tue, 31 Oct 2017 19:00:00 +0530

Technology has advanced, meanwhile software has become powerful. Xilinx & Matlab has worked together to bring hardware cosimulation, where some part of the code will be executing from Xilinx FPGA and input/output can be from Matlab. This is useful for audio, image and signal processing.

This video series describes the Hardware/Software cosimulation of verilog and VHDL coding inside FPGA using Xilinx and Matlab.

Useful SED commands - Linux SED

noreply@blogger.com (Anonymous) — Mon, 30 Oct 2017 22:22:00 +0530

While working in Linux, SED always plays important role in text processing. Here we've given some common examples of SED usage. Hope it will be a life saving that comes in handy!!!!!

Let us know your shortcuts/ commands in comment section below that saved your time...

Linux Commands

Print the number of lines in myfile.txt

sed -n '$=' myfile.txt

-n switch tells SED not to print all lines, which is its default action.

Print lines 5 through 10 from myfile.txt

sed -n '5,10p' myfile.txt

Print all except lines 20 through end of file

sed '20,$d' myfile.txt

Append line numbers to the file. (= prints line number & new line)

sed '=' myfile.txt | sed 's/\n/) /'

Display lines 5-7 and 10-13 from myfile.txt

sed -n -e '5,7p' -e '10,13p' myfile.txt

Display all lines containing 'start'

sed -n '/start/ p' myfile.txt

Add a line after match

sed '/start/ a “MATCH FOUND”' myfile.txt

Add a line before match

sed '/start/ i “MATCH FOUND”' myfile.txt

Change a matching line

sed '/start/ c “MATCH FOUND”' myfile.txt

Display all lines containing beginning 'start'

sed -n '/^start/ p' myfile.txt

To print all the lines after finding the first occurrence of the pattern.

sed -n '/^start/,$ p' myfile.txt

To print 2 lines after finding the first occurrence of the pattern.

sed -n '/^start/, +2 p' myfile.txt

Adds some text before line numbers 3 to 5

sed '3,5 s/^/#/' myfile.txt

To remove blank lines ( ^ denotes start of the line, $ denotes end of line)

sed '/^$/d' myfile.txt

To remove lines starting with 'start'

sed '/^start/d' myfile.txt

To remove lines ending with 'start'

sed '/start$/d' myfile.txt

To remove lines containing 'start' and 'end' (.* stands for any character

sed '/.*start.*end.*/d' myfile.txt

To remove lines starting or ending with '#' or empty lines

sed '/^#\|#$\|$^/d' myfile.txt

To replace multiple blank spaces with a single space

sed '/ */ /g' myfile.txt

To insert one blank line every line

sed G myfile.txt

To insert two blank line every line

sed 'G;G' myfile.txt

To replace every instance of the word version with story in myfile.txt, do:

sed 's/version/story/g' myfile.txt

To ignore character case, use 'gi' instead of 'g'

sed 's/version/story/gi' myfile.txt

To replace words only within a line range (30 through 40, for example)

sed '30,40 s/version/story/g' myfile.txt

To replace words except within a line range (30 through 40, for example)

sed '30,40!s/version/story/g' myfile.txt

To replace only 2^nd match of the search pattern

sed 's/version/story/2' myfile.txt

Emulating dos2unix with inline editing, by removing (^M) from the file created in Windows, and save the output in same file.

sed -i 's/\r//' myfile.txt

Replacing words only if a separate match is found. For example replace to replace 'start' with 'stop' only if the word services is found in the same line

sed '/services/ s/start/stop/g' myfile.txt

Performing two or more substitutions at once in the same file

sed -i 's/that/this/gi;s/line/verse/gi' myfile.txt

To replace a word beginning with uppercase or lowercase with another word, example word 'zip' or 'Zip' with 'rar' in myfile.txt

sed 's/[Zz]ip/rar/g' myfile.txt

To replace a pattern with some text including search pattern.

sed 's/Zip/Create & and send mail/g' myfile.txt

The above command does Zip to → Create Zip and send mail to

Do replacement and write the changes done to a seperate file.

sed 's/Zip/Create & and send mail/w changes.txt' myfile.txt

changes.txt will have “Create Zip and send mail to”

Transform function works similar to replacement, instead it works on the character replacement in place of pattern. For example replace h→H, s→S, i→I, x→W

sed 'y/hsix/HSIY/' myfile.txt

sed '2y/hsix/HSIY/' myfile.txt => performs in 2^nd line

Read function, prints the contents of the specified file in the next line where the pattern is found. For example, when 'NAME:' is found, add the contents of 'namelist.txt'

sed '/NAME:/r namelist.txt' myfile.txt

Switching pairs of words. Lets say, to switch 'first, last' with 'last, first' in the lines starting with 'NAME'

sed 's/^NAME: $\w*$, $\w*$/NAME: \2, \1/g' myfile.txt

sed 's/$\w\+$, $\w\+$/\2, \1/g' myfile.txt

sed 's@$\w\+$, $\w\+$@\2, \1@g' myfile.txt

Valid delimiters can be @ | ! ^

with 's!/dev/null!/dev/stdout!gp' → /dev/null becomes /dev/stdout

useful when the string has '/' characters.

Below table provides the short codes for pattern matching. It is very similar to Perl RegEx.

Code	Description
\w	Alphanumeric Characters including _
\W	Non-Alphanumeric Characters
\s	White Space
\S	Non-White Space
\d	Digits
\D	Non-Digits
.	Any character
*	Zero or more occurrence
\+	One or more occurrence
\?	Zero or one occurrence
\{m\}	Exactly m number of occurrence
\{m,n\}	Within m to n occurrence
\{m,\}	Greater or equal to m occurrence

VERILOG TIMESCALE - TIMEFORMAT - EXAMPLE

noreply@blogger.com (Anonymous) — Tue, 7 Jun 2016 19:16:00 +0530

In this post, let us see the timescale feature and system tasks that are available in Verilog HDL with brief examples.

`timescale directive specifies the time unit and time precision of the modules that follow it. The time unit is the unit of measurement for time values such as the simulation time and delay values.

Syntax: `timescale <time_unit>/<time_precision>

The time_unit argument specifies the unit of measurement for times and delays.

The time_precision argument specifies how delay values are rounded before being used in simulation. The smallest time_precision argument of all the 'timescale compiler directives in the design determines the precision of the time unit of the simulation.

The time_precision argument shall be at least as precise as the time_unit argument; it cannot specify a longer unit of time than time_unit. The integers in these arguments specify an order of magnitude for the size of the value; the valid integers are 1, 10, and 100. The character strings "s, ms, us, ns, ps, and fs " represent units of measurement;

Example: `timescale 1ns/100ps

Here in the above example, time_unit is 1ns & time_precision is 100ps. So the delay of #1 in the code is equivalent to 1ns delay in simulation. The delay of #1.56 will be rounded to 1.6ns. i.e. the decimal fraction will be rounded to in multiples of the time_precision value. Each #delay value is rounded to time delays w.r.t the timescale specified and added to the current simulation time.

Some of the system tasks on timescale are

· $printtimescale() prints the timescale settings of the current scope of the file.

· $timeformat(..,..,,,) system task

The $timeformat system task performs the following two operations:

Ø It sets the time unit for all later-entered delays entered interactively.

Ø It sets the time unit, precision number, suffix string, and minimum field width for all %t formats specified in all modules that follow in the source description until another $timeformat system task is invoked.

Syntax for $timeformat is

$timeformat ( units_number , precision_number , suffix_string , minimum_field_width ) ;

Example: $timeformat(-9,3,"ns",8); This will display any %t string in ns with 3 digits precision, and 8 characters string size.

Let us see the code for the example used for different timescale settings & $timeformat system task.

initial begin

$timeformat(-9,3,"ns",8);

#1 $display("\n1) %t",$realtime);

#10.5 $display("\n2) %t",$realtime);

#10.56 $display("\n3) %t",$realtime);

#10.56 $display("\n4) %t",$realtime);

#11.46 $display("\n5) %t",$realtime);

$finish;

end

The output of the above code with different timescale values are illustrated in the below table.

Timescale	`timescale 1ns/1ps	`timescale 1ns/10ps	`timescale 1ns/100ps
Output	1) 1.000ns 2) 11.500ns 3) 22.060ns 4) 32.620ns 5) 44.080ns	1) 1.000ns 2) 11.500ns 3) 22.060ns 4) 32.620ns 5) 44.080ns	1) 1.000ns 2) 11.500ns 3) 22.100ns 4) 32.700ns 5) 44.200ns

The calculation for timescale 1ns/100ps is as below:

1. Step 1, time is 1ns

2. Step 2, time is (1ns+10.5ns)=11.5ns

3. Step 3, time is (11.5ns + 10.6ns) = 22.1ns

4. Step 4, time is (22.1ns + 10.6ns) = 32.7ns

5. Step 5, time is (32.7ns + 11.5ns) = 44.2ns

Similarly you could calculate for different timescale values. If you've any queries, plz do comment it.

If you enjoyed this post plz let us know your views via comments.
This helps us to do much more better.
Thankyou.

Perl – File Read Write Example

noreply@blogger.com (Anonymous) — Tue, 5 Apr 2016 10:57:00 +0530

Perl – File Read Write Example

In this post, let’s see how to remove the new line character or line break in a text file and save the result in another text file.

Refer to other posts File handling, RegEx.

To accomplish the removal of new line character, we use RegEx substitution operator. The code for substitution is as below,

$a =~ s/\n//; # $a is the variable in which the replacement takes place

· The input to the script is through command line arguments. The command line inputs are stored in the array variable @ARGV (please note the CAPS). First we check the size. If no command line arguments is specified, the size of ARGV is -1. If so, the script prints the usage & exits, using the in-built function die().

unless($#ARGV <0) {

$in_file=$ARGV[0];

} else {

die "\nUsage:\n remove_new_line.pl <input_file>\n";

}

· If valid input is provided, then open the specified file in read mode as below. If unable to open the file, exit with a note printed. $! Is the Perl system variable which prints the error from the OS.

open FIN, "<$in_file" or die "Unable to read '$in_file' :$!";

· Create the output file by appending the name “new_” to the input file name.

open FOUT, ">new_$in_file" or die "Unable to create 'new_$in_file' :$!";

· Then create a loop, that executes for each line of the input file. Then remove the newline character and write back the result to output file.

while ($a=<FIN>) {

# remove \n character

$a =~ s/\n//;

# write the new data to text file

print FOUT $a;

}

Sample output of this script:

Top file is the input & bottom file is the output.

Click here to download this script.