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Altera_Forum's avatar
Altera_Forum
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15 years ago

Fast Output Enable

I've got 16 bidirectional pins and I want the registers as close as possible to the pad to cut down on any routing delays between the last register and the pad on the output side and the first regist...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
15 years ago

I'm using Quartus 9.0sp2.

Once I replicated the register manually I used QSF constraints to try to preserve the replicated OE registers:

set_instance_assignment -name PRESERVE_REGISTER ON -to *dat_ena*

set_instance_assignment -name REMOVE_DUPLICATE_REGISTERS OFF -to *dat_ena*

What was weird was that they still got optimized out.

However, the point is now moot, I was able to get the tool to replicate the register for me. I changed the logic back to having just a single output enable and it appears to be working correctly now although I'm not immediately sure what I did to fix it. Perhaps I had a code problem somewhere although I could see the path in timequest and there was no logic between the register and the pad but I must have been doing something wrong somewhere.