From: Clifford E. Cummings (cliffc@europa.com)
Date: Fri May 02 1997 - 09:08:58 PDT
Subject: BTF - B20 - Pullup/pulldown optional X-drive time
Behavioral Task Force - Enhancement Request
Assigned Enhancement Request Number: B20
Enhancement Name (Description): Pullup/pulldown optional X-drive time
Date Submitted: 970418
Requestor: austen@ixia.com (Austen Hypher)
Status: RO
Is enhancement intended to be synthesizable?:
I would like to suggest therefore that the pullup/down models be modified
to accept an optional time (hence backwards compatible) and to have them
drive an x for that time before driving the final pulled state.
There exist in verilog pullup and pulldown primitives. These are useful,
but I have found them to be inadequate for simulating PCBs because the
transition from the driven state to the pulled state is instantaneous
in the verilog primitive.
In the real world there is a period of uncertainty after the driver
switches off and before the line has transitioned to the pulled state.
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