Re: [IBIS-Users] Comments on 18 teleconference BIRD95.

Hello Itzik, my comments in-line - Syed

On Sun, 2005-02-20 at 08:27, Itzik Peleg wrote:
> Hello IBIS users.
> 
>  
> 
> BIRD 95: 
> 
> (I noted this in the conference but I think I wasn’t understood.)
> 
> The SSN effect on timing is very important in system simulations. In
> the IBIS summit we had seen some presentations about BIRD 95 and his
> ability to model correctly the power bounce on the vdd pin.
> 
> I think this is very important but also important is the influence on
> the buffer output signal in terms of delay and edge rate degradation.
> Arpad has raised this at the end of the BIRD 95 discussion in the
> summit (gate modulation effect). I think that we should consider
> adding more effects that are due to pre-drive circuit and can
> influence the buffer output. Gate modulation is one of the effects.
> But pre driver can suffer from voltage drop in many ways such as:
> added delay to his logic circuit, driving less then a complete ‘0’ or
> ‘1’ example: when having a one buffer driving opposite pattern in a
> bus. When this buffer is trying to drive high, the rest of the bus
> drives low. As a result there is a ground bounce which affects the
> buffer (the single one) pre drive (the pre drive last stage drives
> opposite then the buffer – the single buffer drive high so his
> pre-drive drives low). Instead of the pre drive driving 0 its driving
> something above 0 due to the ground bounce noise and we get a wicker
> drive strength and probably different delay in the output pin.
> 
>  

BIRD95.1 handles many of the first order effects very well. Gate
modulations effect, as per discussion on the 18th teleconference will be
addressed as a separate BIRD.

> 
> My point is: since IBIS 2.1 spec (and v(t) curves) we have 3 cases
> when the buffer behavior is capture (under the assumption of ideal
> power supply).This 3 cases are correct in term of pad delay due
> nominal voltage changes (as describe in the ibis file). The delay
> information was in the v(t) curves relations.  I think that when
> stepping forward to SSO we need to ensure that the timing effect on
> the pads output is capture within the IBIS (and this should be general
> enough to capture all effects).
> 
> This is open for comments.
> 

One of the major advantage of BIRD95.1 interms of SSN is to quantify the
SSN Clk push-out/push-in effects in timing. Currently we are splitting
the BIRD95.1 into three segments in order to address each respective
sections effectively so we can move forward and reach closure soon.

If you have specific areas of BIRD95.1 to address, pls do bring that up
and we shall resolve them with all your support. We can always generate
a new BIRD depending on the scope of any new proposals.


>  
> 
> --
> Regards
>  
> Itzik Peleg
> Board Technology Group
>  
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