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Altera_Forum's avatar
Altera_Forum
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17 years ago

Counter Problems

Hi, im trying to implement a counter which counts positive, negative, or both edges of an incoming signal. It works, but if I give 10000pulses to it it counts only between 9980...9997. The interna...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
17 years ago

I'd add to Kaz's reply by saying that I'd pass in_signal through two registers and not present the "raw" unsynchronised signal to any logic, in order to avoid metastability: 

in_signal_d <= in_signal;
in_signal_dd <= in_signal_d;

and then: 

if in_signal_d /= in_signal_dd then
...

(I'd also probably separate the code out into two processes but that's just my personal preference).