( ESNUG 368 Item 8 ) --------------------------------------------- [04/12/01]
From: Farhan Shahid <fshahid@vt.edu>
Subject: The VCD Viewer In VSS Doesn't Show Correct Intermediate Bus Values
Hi, John,
I am trying to dump VCD files through the VSS VHDL simulator. By using the
command vcdaddobjects 0 TEST_BENCH/*'sig, and then "vcddumpall". I am able
to dump all the signals except individual signals for buses which are
dumped as HEX values. The VCD viewer howvever does not show the correct
intermediate value for buses.
For example if one signal in the bus is delayed for 2 seconds, and the
second for 3 seconds, the intermediate value between 2 and 3 sec (the
hazard) is not shown correctly. A sample virsim view would be like this
Time (sec) 14 15 16 17 18 19 20
C[1:0] |0.. |1... |1.. |2...
-------------------
C1 (correct) _____________________|
--------------
C1 (expanded) __________________________|
----------------------
C0 (correct) _____| |_____________
----------------------
C0 (expanded) _____| |_____________
The actual value shown between 18 and 19 should be 3 here, rather than 1.
Note that the individual signals are also not displayed properly when
expanded through virsim. If I use the -split_bus option,the individual
signals are though displayed correctly but I am unable to combine them
into a bus again, specially when using other viewers.
Can any one guide me about the source of the problem & how to correct it?
- Farhan Shahid
Virginia Tech.
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