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Collection of Hack-Phreak Scene Programs
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FPGAWKII.ZIP
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PRODUCT.PDS
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1995-02-15
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; This example demonstrates situations
; where the PLDshell design compiler can
; and cannot fit a design to the EPX780
; due to constraints on the number of
; product terms that a macrocell can
; access. Essentially, o1 and o2 are
; sum-of-products outputs with 8 product
; terms each. If they are assigned to
; adjacent macrocells, the design will
; not fit because there are not enough
; product terms to share. If you move
; o2 slightly farther from o1, then there
; are sufficient product terms to share
; and the design will fit in the EPX780.
;
; SET COMPILER OPTIONS TO:
; Use Design Pin Assignments, but not
; Previous, Abort on no fit
CHIP product NFX780_84
PIN a[0:7] ; eight inputs
PIN 82 o1 ; first output
;second output adjacent to o1
;PIN 83 o2 ; second output (no fit!)
; second output not adjacent to o1
PIN 84 o2 ; second output (this fits!)
EQUATIONS
o1 = a0*a1 + a1*a2 + a2*a3 + a3*a4 +
a4*a5 + a5*a6 + a6*a7 + a7*a0
o2 = a0*a3 + a1*a4 + a2*a5 + a3*a6 +
a4*a7 + a5*a0 + a6*a1 + a7*a2