Answers Database

XABEL, Foundation F1.3/F1.4: BLIFOPT step runs indefinitely during ABL2EDIF


Record #3007

Product Family:  Software

Product Line:  Data I/O

Problem Title:
XABEL, Foundation F1.3/F1.4: BLIFOPT step runs indefinitely during
ABL2EDIF



Problem Description:
Keywords: ABEL, ABL2EDIF, BLIFOPT, HDL Editor, comparator

Urgency: Standard

General description:
In Foundation  F1.3, HDL Editor, when running Synthesize on a
large ABEL design, the ABL2EDIF process is invoked, the
AHDL2BLF step completes, the BLIFOPT step begins but never
completes. One possible cause is that the design contains some
large comparator logic (of the form Y = A == B). This problem
also occurs under Synario v3.00.


Solution 1:

In the ABEL source, decompose any equations containing
comparator logic by separating out the comparator logic into
new intermediate node equations. Express the intermediate node
equations as active-low comparators of the form NOT_Y = A != B.
Also, prevent collapsing of the intermediate nodes by applying
the attribute KEEP.

For example, if the original equation is:

  Q = (A == B) & something # (C == D) & smore ;

Decompose into:

  A_ne_B = (A != B);  "new node
  C_ne_D = (C != D);  "new node
  Q = (!A_ne_B) & something # (!C_ne_D) & smore ;

Then declare the new nodes with the KEEP attribute, as in:

  A_ne_B, C_ne_D node istype 'KEEP';



End of Record #3007