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Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
9 years ago

Does the alt_u16 type support 0xFFFF or not?

Please consider the following code: 


...
alt_u16 i;
....
for(i=0x0000; i<=0xFFFF; i++)
...

I am getting the following warning during my compilation:

comparison is always true due to limited range of data type

To temporarily solve this I changed the upper limit from 0xFFFF to 0xFFFE

My questions are:

  1. Why this is happening? I ask this because I was thinking that the alt_u16 as an unsigned 16 bit could fit the 0xFFFF

  2. Do I need to increase the type alt_u16 to alt_u32 only to support one additional bit or how can I solve this problem?

2 Replies

  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    9 years ago

    alt_u16 can hold 0xFFFF, but it can't hold anything larger than that. So the comparison "<= 0xFFFF" is always true. Which is exactly what the compiler is telling you the problem with your code is.

    You can use an alt_u32 to keep the rest of your for() loop the same as already written.
  • Altera_Forum's avatar
    Altera_Forum
    Icon for Honored Contributor rankHonored Contributor
    9 years ago

    --- Quote Start ---

    alt_u16 can hold 0xFFFF, but it can't hold anything larger than that. So the comparison "<= 0xFFFF" is always true. Which is exactly what the compiler is telling you the problem with your code is.

    You can use an alt_u32 to keep the rest of your for() loop the same as already written.

    --- Quote End ---

    thanks again, ted