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AR# 7470

FPGA/Design Compiler: Bi-directional I/O has extra inversion inferred (IOBUF_N)


Keywords: Synopsys, Compiler, libraries, xc4000, IOB, inversion, IOBUF_N

Urgency: Hot

General Description:
When creating a bidirectional I/O, Synopsys Design Compiler or FPGA Compiler will
use an IOBUF_N component. With Xilinx version 1.5i or earlier, this represented a
standard bidirectional I/O with no inversions, but that functionality changed with 2.1i,
as inversion was now introduced on the input buffer.

This results in a functionally incorrect netlist.


This problem is fixed in the latest 2.1i Service Pack available at:
AR# 7470
Date Created 09/08/1999
Last Updated 08/31/2001
Status Archive
Type General Article