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AR# 2428

5.x HMGEN - What is HMGEN?


Keywords: hard macros, xc4000, hmgen

Urgency: Standard

General Description: In the app note, "Improving xc4000 Design Performance", a
program called HMGEN. What is HMGEN?


HMGEN was a program that constructed .hm files (hard macro files) from .LCA
files. It has since been replaced by RPMs, so it is obsolete.

HMGEN is an old program, and one that is not recommended anymore, nor is
there future support for it. The reason is basically that it reduces the
flexibility of PPR, and essentially "locks" up parts of your design. Most
users want to keep the routing of certain blocks consistent.
However, HMGEN will create a Hard Macro from the "unrouted" LCA file. So,
there will be no routing information in it, just placement information.

For this reason, you may want to consider using the RLOC properties. These
RLOC properties tell PPR the "relative placement" of certain parts of the
design. It constrains logic relative to other logic, but doesn't constrain
the group to a particular place on the device. These grouped sections of
logic can remain "just this logic", or you can allow PPR to insert other logic
into available spaces in the CLBs in these groups. This enables PPR more
flexibility, "if you wish", or, if you'd rather PPR did not touch these
portions of the design, you can also tell it that. Please refer to
pages 4-71 - 4-94 of the "Xilinx Libraries Guide" for more information on RLOCS.

Currently, this is the recommended design flow.
AR# 2428
Date 03/22/2000
Status Archive
Type ??????
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