Answers Database

What kinds of information IBIS Models do and don't provide.


Record #3359

Product Family:  Software

Product Line:  FPGA Core

Problem Title:
What kinds of information IBIS Models do and don't provide.


Problem Description:
KEYWORDS: ibis, spice, i/o characterization

URGENCY:Standard

GENERAL DESCRIPTION: IBIS models provide information on I/O characteristics. IBI
S models can be freely distributed to any customers who request them because the
se models do not require Xilinx to reveal any proprietary device technology data
.


Solution 1:

IBIS CAN:

1. model best case and worst case models by using the min, max current w/the pro
per min, max ramp rates.

2. model SSO (Simultaneous Switching Output). These are mainly the package induc
tance, other associated parasitics and the number of buffers switching. IBIS spe
cifies R, L and C in matrix format and the use of a matrix for the inductance ac
counts for the "loop"inductance i.e. the mutuals between the pins. Specifying th
e mutual inductance is necessary to account for SSO event simulation.

3. (v2.1) model RTC(Rise Time Controlled), GTO(Gradual Turn on) or Slew rate con
trolled outputs. These are defined under [Rising Waveform] and [Falling Waveform
] keywords.

4. model ground bounce. IBIS contains the the package parasitic information nece
ssary to simulate ground bounce. Even though the data is available within the mo
del file, not all simulators may be able to use it to simulate ground bounce. Re
fer to your respective simulator for support.

IBIS CAN'T:

1. provide timing information (i.e. propdelays, skew, etc).

2. support measurement of propagation delays. IBIS is mainly used to simulate tr
ansmission lines and analyze signal integrity issues.



End of Record #3359