how to divide a number by 1000 in FPGA

[arash rezaee]

Hi everyone

I have 16bit number which represent amplitude of my project and I want to divide it by 1000 and then multiply it with 0.16. How can I divide with a number which is not in the power of 2?

Please help me.

Regards
Arash

 

[FvM]

Literally, a divider can be used. But the "multiply it with 0.16" point suggests that you are not talking about integer numbers. Thus I think, you should clarify first about the involved number formats.

Multiply with 0.001 would be a correct answer as well ...

 

[Jansi Meena]

IN VHDL\Verilog is divisor allowed?....All I know is repeated subtraction for division in case of integers not in power of 2

 

[childs]

Why not just multiply it with 160 instead of divide by 1000 then multiply by 0.16?
Anyway, I suppose divide can be done by using numeric_std library.

 

[TrickyDicky]

even better, use multiply from the fixed point library. divide is doable but needs a decent pipeline to workand you wont get that from a divide funtion. you need to use a divide ip block.

fixed divides are the same as a multiply

 

[arash rezaee]

Thanks for reply
first of all I want to divide it by 1000. Then multiply it with 16 and at the end divide it by 100. How can I divide it? because when I divide it by 1000 the synthesiser got error and said it must be power of two.

any suggestion?

---------- Post added at 09:40 ---------- Previous post was at 09:37 ----------

Why not just multiply it with 160 instead of divide by 1000 then multiply by 0.16?
Anyway, I suppose divide can be done by using numeric_std library.

Do you really think 0.16 divide by 1000 is 160?? It is 0.00016 anyway

 

[TrickyDicky]

just muliply by 0.00016. look into fixed point notation. forget about divide.
vhdl has fixed point package to help with this.

 

[arash rezaee]

just muliply by 0.00016. look into fixed point notation. forget about divide.
vhdl has fixed point package to help with this.

Would you mind explain more? I don`t know this package and also I don`t know how to use it.

Regards

 

[TrickyDicky]

first of all, I suggest reading up on fixed point:
https://en.wikipedia.org/wiki/Fixed-point_arithmetic

then have a look at the fixed point package for VHDL (it became part of the VHDL 2008 standard)
you can get a user guide and 93 compatible versions here:
www.vhdl.org/fphdl

 

[gongdori]

Unless you divide by 2^x, It is not easy thing to do. In general, division is avoided. In your case, you can multiply by (0.16/1000). Then, it can be done by using a multiplier.
If your work allows you to divide by 1024 instead of 1000, it can be done without using any resource.

 

[arash rezaee]

first of all, I suggest reading up on fixed point:
https://en.wikipedia.org/wiki/Fixed-point_arithmetic

then have a look at the fixed point package for VHDL (it became part of the VHDL 2008 standard)
you can get a user guide and 93 compatible versions here:
www.vhdl.org/fphdl

I am using ISE12.1 and I search in xilinx directory. I found that I have IEEE-PROPOSED in there. but when I write these two code ISE got error.
two lines are :
library ieee_proposed;
use IEEE_PROPOSED.FIXED_PKG_c.ALL;

what can I do now?
Regards

 

[TrickyDicky]

have you included the fixed package souce code in the project?
what exactly was the errror?

 

[arash rezaee]

have you included the fixed package souce code in the project?
what exactly was the errror?

How can I include it? I really don`t know how to include package to library. will you please elaborate it for me.

 

[TrickyDicky]

just add the source files to your project file list.

 

[arash rezaee]

I did it. but nothing changed. I have the error. Have you ever worked with divider ip core of ISE?

 

[FvM]

I wonder if it's of much use to discuss unsaid errors from unknown code?

 

[arash rezaee]

I added to my project and when I run synthesis the same error I mention above appeared again.

 

[FvM]

the same error I mention above appeared again

May be it's my eyes. Can you please tell the post number where you reported the error message?

Did you mean post #11 "ISE got error!" :lol:

 

[arash rezaee]

May be it's my eyes. Can you please tell the post number where you reported the error message?

Did you mean post #11 "ISE got error!" :lol:

))))
I thoutgh I mentioned about the error but I just mentioned about the library. you are right
this is code for using library:
library work;
use work.fixed_pkg_c.all;
this is the error :
ERROR:HDLParsers:3014 - "D:/Generator/i2stransmitter/AMPCONVERT.vhd" Line 28. Library unit fixed_pkg_c is not available in library work.

 

[TrickyDicky]

try
use work.fixed_pkg.all;

instead. The package name is not the file name.