how to know while loop number of iteration ?

hey there ,
so in my code i need to know how many times a while loop was excuted (i don't know the number of iteration in advance and i should know it in a division algorithm )
how to know the value of I outside the process in the following example ?

i'm a newbie please help me and excuse my english

3 comments after a casual glance.....
1. You are doing a comparison between x and b but have not included x in the sensitivity list.
2. Avoid using 'while' loop (if this piece is used for non-synth part of the design, then ok with while loop)
3. I am assuming 'I' is storing the no. of iterations. So declare it as signal and then use it accordingly if you want to use it in another process.

dpaul said:

3 comments after a casual glance.....
1. You are doing a comparison between x and b but have not included x in the sensitivity list.
2. Avoid using 'while' loop (if this piece is used for non-synth part of the design, then ok with while loop)
3. I am assuming 'I' is storing the no. of iterations. So declare it as signal and then use it accordingly if you want to use it in another process.

Click to expand...

thanks a lot,i'm sorry for making such horrible mistakes,i need to synthesis this code,i'm going to do a number of repeated substraction until i reach a certain condition (for example a>b ..) so can you give me a suggestion in whish structure should i use to do that,knowing that i'm dealing with signed numbers thanks a looot !

jojo26 said:

thanks a lot,i'm sorry for making such horrible mistakes,i need to synthesis this code,i'm going to do a number of repeated substraction until i reach a certain condition (for example a>b ..) so can you give me a suggestion in whish structure should i use to do that,knowing that i'm dealing with signed numbers thanks a looot !

Click to expand...

Counters (along with terminal count compares) are typically used in hardware designs to determine how many times you do something.

Hi,

i'm going to do a number of repeated substraction until i reach a certain condition

Click to expand...

define the (valid) ranges for "x", "r" and "b".

***
imagine "r" = 0.
then neither "x" nor "b" will be changed in your loop.
--> the loop will be infinite.

Klaus

The code can't be synthesized anyway due to unconstraint iteration count.

I presume it's based on the popular misunderstanding that an iteration loop defines a sequence in time. But it's only sequentially executed in simulation. In synthesis it instantiates parallel logic. Because the iteration count can't be determined at compile time, it's dropping a synthesis error.

In cases where you actually want to generate parallel logic by an iteration construct, the compiler must know how many instances. A for next loop will tell this by its fixed range.

As ads-ee explained, a sequential divider will use a loop counter and a clock. Under circumstances you can define a parallel divider by an iteration construct. But it would be better generated in a hierarchical structural description.

can you recommand any book or tutorials that can help me understand how a design work on hardware ? when it can be synthesizable and when not and why ? i feel like it's hard to write VHDL with my basic electronics knowlege
i'm so grateful,thanks for your answers
regards jojo