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question about D flip-flop

Altera_Forum
Honored Contributor II
‎09-21-2011 10:46 PM
10,358 Views

Hi all, 

 

I am wondering what does the PRN port in the D flip-flop used for? 

When PRN is deasserted, the output always stay asserted.Thanks!
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Altera_Forum
Honored Contributor II
‎09-21-2011 10:54 PM
6,329 Views

It is the preset, when preset = 0, DFF.Q = 1

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Altera_Forum
Honored Contributor II
‎09-22-2011 03:04 AM
6,329 Views

Thank you!But what does preset used for?

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Altera_Forum
Honored Contributor II
‎09-22-2011 05:41 AM
6,329 Views

it is the opposite of clrn

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Altera_Forum
Honored Contributor II
‎09-22-2011 06:31 AM
6,329 Views

Thank you!But why we need preset?

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Altera_Forum
Honored Contributor II
‎09-22-2011 07:23 AM
6,329 Views

the same reason you need clrn, but you want to reset to '1'.

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