Achronix ACE Version 5.0 - Manual (Page 294)

Managing I/Os Chapter 4. Tasks
Managing I/Os
I/O electrical properties are often iteratively tweaked at the final stages of design. Frequently the user does
not want to alter their source RTL to make these changes, because doing so would necessitate re-running
the entire Flow.
The IO Assignment view was created to ease these last-minute tweaks. This view allows I/O electrical
changes to be made without impacting the PnR. The user can iteratively tweak electrical settings, regenerate
the Bitstream, and test, repeating until the design performs as desired. The user can then save off the set
of changed property values in an
.sdc file (see Save Changed Properties dialog ). This .sdc file may be
added to the project as a design constraint file, or the desired property values contained in the file could be
integrated back into the source RTL.
In addition to the IO Assignment view , there are design rule checks that ensure all I/O instance parameters
are valid. These checks are run at several points in the Flow, and will help ensure that the user does not
create a Bitstream with any invalid I/O configurations.
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