Article View: comp.lang.vhdl
Article #315wire primitives in VHDL
From: George Lippincott
Date: Tue, 22 Dec 1992 01:45
Date: Tue, 22 Dec 1992 01:45
32 lines
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1578 bytes
I am trying to figure out a way in VHDL to merge two bidirectional signals into one signal. This is something that most of the major logic simulators let you do but which as far as I can tell is impossible in VHDL. This situation comes up when an entity is implemented in such a way that two bidirectional ports connect to the same signal. What I would like to do is have some way to "short" these two signals together. Ideally the resolution function would see all of the drivers for both signals and calculate a value for both nets. This can be done in Verilog like this: module wire(w,w) inout w; endmodule; I haven't been able to figure out a way to do the same thing in VHDL. If I use the code: a <= b; b <= a; Then a driver is added to both signals and the value gets stuck at 'U' due to the nature of the resolution function in the IEEE 1167 package. Does anyone have any idea on how to work around this? --------------------------------------------------------------------------- George Lippincott | UUCP: uunet!ole!george Cascade Design Automation Corp. | Internet: george@ole.cdac.com 3650 131st Ave SE, #650 | TEL: (206)-649-7661 Bellevue, WA 98006 | FAX: (206)-649-7600
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Newsgroups: comp.lang.vhdl Path: arc1-ca.pugleaf.net!sparky!uunet!nwnexus!ole!george From: george@ole.cdac.com (George Lippincott) Subject: wire primitives in VHDL Message-ID: <1992Dec22.014551.24293@ole.cdac.com> Organization: Cascade Design Automation Date: Tue, 22 Dec 1992 01:45:51 GMT Lines: 32