All,
In the Beginning:
The die-pad and buffer where shorted together.
[External Model] did not change this.
Timing and Voltage rules were assumed at the die-pad or the pin.
This is also true in IBIS 6.1
With BIRD 189, and anticipating The C_Comp BIRD, there are the following
potential nodes in a simulation:
1. Pin
2. Die-Pad
3. “Buffer Side” of on-die interconnect
4. “Buffer Side” of on-die S-Parameter
5. “Buffer Side” of C_comp Circuit
6. Latch
In IBIS 6.1 the user can select “Die” or “Pin” for the [Component] Keywords
Si_location and Timing_location.
IBIS has always be intended to be an electronic data sheet for a component.
All component data sheets that I have seen generally give rules at the pin,
while some data sheets have rules at the die-pad. I have never seen a data
sheet that has rules at the buffer.
Question, We have member of this committee and IBIS who develop high speed
memories, controllers and SerDes IP. Do any of these companies have plans of
releasing IP or Component data sheets that have rules at the buffer instead
of the die-pad or pin (except of course rules at the latch in AMI Models)?
The only issue that we need to deal with is package models in BIRD 189 that
are between pin and buffer. Since the model maker did not make a model from
pin to die, then the buffer terminal must be assumed to be shorted to the
die, and therefor Si_location or Timing_location set to die must be
interpreted as same as the [Model] signal terminal. Note that in this case
of on-die s-parameter or in the future C-Comp circuit BIRD this will be on
the die side of the these circuits.
I do not think that it is necessary to add this explanation to IBIS, but it
would not hurt to replace the content of BIRD 191 with the above translated
to IBIS-Speak.
I understand the desire to enhance IBIS to allow timing and Si at the buffer
instead of the die pad, but this would fall into the category of pre-mature
optimization and would require EDA tools to make enhancements unnecessarily.
Walter
