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Altera_Forum
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14 years ago

Quartus II and the funny synthesis attributes

Hi everyone, Last week I noticed some funny results after the implementation of my desing in Quartus II 11.0. Inside it there are two simple register chains, each one made up of three registers o...
Altera_Forum's avatar
Altera_Forum
Icon for Honored Contributor rankHonored Contributor
14 years ago

Ive had exactly this issue, with much worse problems. I had a single bit x7 registers in behavioural code, and it would take 1 M9k per filter I generated (which was 32!!!!). The problem is the altshift_taps megafunction, because it has a habit of using M9Ks for no good reason.

The reply I got from mysupport:

"i have however discovered a solution using the analysis and synthesis options, more settings, and setting auto shift register replacement to “off”, by default this is “auto”. you can navigate to the option, in assignments, settings, analysis & synthesis setting, more settings. auto shift registers to “off”

alternatively you can simply add the following line to your qsf file.

set_global_assignment -name auto_shift_register_recognition off"

This should stop it creating altshift_taps and eating all your m9ks