Subject: RE: [IBIS-Users] BIRD84 - Driver Schedule Clarifications
From: Beal, Weston (weston_beal@mentorg.com)
Date: Wed Oct 01 2003 - 13:59:13 PDT
Arpad,
The important bit I get out of this explanation is that the simulator stimulus edge does not constitute and event. An event is a stimulus applied to the scheduled driver as specified by the delays in the driver schedule syntax. I think this is an important definition to include in the BIRD.
Thanks,
Weston
-----Original Message-----
From: Muranyi, Arpad [mailto:arpad.muranyi@intel.com]
Sent: Wednesday, October 01, 2003 10:12 AM
To: ibis-users@eda.org
Subject: RE: [IBIS-Users] BIRD84 - Driver Schedule Clarifications
Weston,
Thanks for your comment and question.
I have to ask you a question before I can answer yours. What is in the
Fall_on/off_dly parameters in your example? NA or 0?
If they are both NA, then there are no "events" generated by a falling edge
stimulus. Having said that, using your numbers the rising edge will turn on
the pullup 1 ns after the stimulus went high and at the same time turn off
the pulldown. Using the same rising edge stimulus, the 15 ns rise off delay
parameter will turn off your pullup 15 ns after this rising edge stimulus
went high, and at the same time turn on the pulldown. Nothing will happen
until the next rising edge stimulus arrives. The falling edge stimulus is
ineffective.
On the other hand, the situation would be different if there was a zero in
the Fall_on_dly (or Fall_off_dly) parameter. Note, however, that it doesn't
make sense to use zero for both Fall_on and Fall_off parameters at the same
time!!! Also note that there are only 5 combinations of NAs and numbers which
are permitted by the spec. For this reason, the next two conditions are
hypothetical, but I will go through them to make the point clear.
Let's see what would happen if the Fall_on_dly was zero, and the Fall_off_dly
still an NA:
The pullup would turn on 1 ns after the first rising stimulus and at the same
time the pulldown would be turned off. The falling edge stimulus would immediately
turn off the pullup and turn on the pulldown (at 10 ns) because of the 0 delay
in the Fall_on_dly parameter. The 15 ns off delay in the Rise_off_dly parameter
would just redo this same thing, but since the "another event", i.e. the falling
edge stimulus already did that, nothing would happen at 15 ns.
Now, if the Fall_on was NA and the Fall_off zero, the pullup would turn on 1 ns
after the first rising edge stimulus, and the pulldown would be turned off at the
same time. The falling edge stimulus would immediately want to turn on the pullup
and turn off the pulldown, but the "another event", i.e. the previous rising edge
stimulus already did that, so nothing will happen at 10 ns. However, the 15 ns
Rise_off delay is still ticking, so at 15 ns after the first rising edge stimulus
the pullup will be turned off and the pulldown will be turned on.
Now that I think of the BIRD I just wrote, I wonder whether the definition of "event"
should mean that the timer gets reset by the falling edge in this last case or not.
I have to think about that. Other than that, does this answer your question?
Thanks,
Arpad
==================================================================================
-----Original Message-----
From: owner-ibis-users@eda.org [mailto:owner-ibis-users@eda.org]On
Behalf Of Beal, Weston
Sent: Wednesday, October 01, 2003 8:41 AM
To: ibis-users@eda.org
Subject: RE: [IBIS-Users] BIRD84 - Driver Schedule Clarifications
Arpad,
Thanks for doing this work. It helps get everyone working to the same spec. It is still a bit ambiguous to me what happens when a simulator stimulus edge occurs before a delay_off time. For example, if my driver schedule specifies a rise_on_delay of 1ns and a rise_off_delay of 15ns and the high pulse time from my simulator is 10ns. Does the model switch to a low state 10ns after the rising edge or 15ns after the rising edge? I would expect it to switch low at 10ns and I think (but it's a bit ambiguous) that "if they were not already turned ON and OFF, respectively, by another event" means that the simulator stimulus falling edge would cause the model to switch low. Is that how you interpret it and think that was the original intent?
thanks,
Weston
-----Original Message-----
From: Mirmak, Michael [mailto:michael.mirmak@intel.com]
Sent: Tuesday, September 30, 2003 5:07 PM
To: ibis@eda.org; ibis-users@eda.org
Subject: [IBIS-Users] BIRD84 - Driver Schedule Clarifications
All,
The following proposed BIRD, number 84, is submitted on behalf of Arpad
Muranyi of Intel Corporation.
- Michael Mirmak
Intel Corporation
Chair, EIA/IBIS Open Forum
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