Community
cancel
Showing results for 
Search instead for 
Did you mean: 
Altera_Forum
Honored Contributor I
949 Views

Basic example of lpm_counter1 disabled when in overflow

Hi all I need to have a counter that when overflows is set to a predefined value and stops counting. Then only an external signal of clear can restart (from 0) the counter.  

I thought to use the carry out of lpm_counter1 to disable the counter and a DFF to store carry out until a synchronous clear arrives. 

The carry out is also used as a synchronous set for the counter.  

From the simulation the DFF does not behave as expected and it changes its output not following its input nor clock... 

I attach here a screenshot of design and simulation. 

I would be glad you could give me some suggestions.. 

Regards
0 Kudos
2 Replies
Altera_Forum
Honored Contributor I
53 Views

carry_out (the overflow) never goes high because you're clearing the counter before it ever has a chance to, at least in the simulation waveform you show here. Since you're using it as the clock for the dff (a big no-no since you're creating a gated clock; put it on clock enable for the dff instead), the output of the dff is dictated only by the A_clear signal.

Altera_Forum
Honored Contributor I
53 Views

I jumped to same conclusion but indeed I was not able to find a solution to that! 

Now thanks to you it is showed here: DFFE!  

Thanks a lot
Reply