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AR# 4408

A1.4/F1.4 MAP - 3K mapper incorrectly reports unconnected inputs to IFDs and then trims the component.

説明

This problem only occurs when you have the "Q" pin of an input
flipflop or latch directly driving the "IN" pin of an OBUFT
with *no* intervening logic. The IFD will sometimes be sucked
into the output IOB, the connection to the IPAD is lost, and
it all gets incorrectly trimmed because there is no driver.

IFD OBUFT
IPAD ____ OPAD
__ | | |\ __
| |_____| |____| \____| |
| | | | | / | |
-- |> | |/| --
---- __|

ソリューション

This issue is scheduled to be fixed in the M1.5 Performance Pack.
Meanwhile, it can be worked around by inserting a buffer between
the IFD and OBUFT. The buffer prevents the error, but is eventually
optimised away, so there is no performance loss.


IFD BUFFER OBUFT
IPAD ____ OPAD
__ | | |\ |\ __
| |_____| |____| \____| \____| |
| | | | | / | / | |
-- |> | |/ |/| --
---- __|
AR# 4408
作成日 08/05/1998
最終更新日 04/03/2000
ステータス アーカイブ
タイプ 一般