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Constraints for mem_reset_n in DDR3 IP

Altera_Forum
Honored Contributor II
‎07-09-2013 05:58 PM
1,182 Views

Anyone tried to constraint the mem_reset_n signal? 

 

We were having some odd issues with timing and so I was going through clearing up warnings. It sometimes fixes problems, and unfortunately the memory IP and the PCIE IP can produce quite a bit of them, and some look scary too. I guess they must be false as the IPs are in use in industry, but it could have been cleaner, so real warnings do not get overlooked. 

 

Anyways I came accross the unconstrained paths in Timequest. There were several in the code I am working on and I checked the example and saw the same thing. After specifying all reset synchronizers as false paths (there are several scattered around the IPs), and defining constraints given in the Altera documentation for the tck related signals I got the unconstrained paths down to just mem_reset_n. The tool still says it has no input/output max delays specified. Anyone got any ideas?
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Altera_Forum
Honored Contributor II
‎07-09-2013 06:59 PM
506 Views

 

--- Quote Start ---  

Anyone tried to constraint the mem_reset_n signal? 

 

We were having some odd issues with timing and so I was going through clearing up warnings. It sometimes fixes problems, and unfortunately the memory IP and the PCIE IP can produce quite a bit of them, and some look scary too. I guess they must be false as the IPs are in use in industry, but it could have been cleaner, so real warnings do not get overlooked. 

 

Anyways I came accross the unconstrained paths in Timequest. There were several in the code I am working on and I checked the example and saw the same thing. After specifying all reset synchronizers as false paths (there are several scattered around the IPs), and defining constraints given in the Altera documentation for the tck related signals I got the unconstrained paths down to just mem_reset_n. The tool still says it has no input/output max delays specified. Anyone got any ideas? 

--- Quote End ---  

 

 

You can constrain a reset just like any other input. 

If you decide to resynchronise it then you can set false path: 

set_false_path -from [get_ports {mem_reset_n}]
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