3COM IBIS MODEL STANDARD

Subparameter of [ Pin Numbers ]. These are the properties for each section of the stub on a pin in a package. For example, if the length of the section is 2 ‘units’ and the inductance is 1.5 nh / unit, then the inductance of the section is 3.0 nh. If a Len of zero is specified then the L/R/C values are the total for the section. If Len  0, then the total L/R/C for that section is multiplied by that value. However, then the L/R/C should be treated as distributed elements. A package stub can include, but is not limited to, the pad to pin bondwire. A package stub begins at the connection to the die and ends at the point where the package pin interfaces with the board or substrate the package IC is mounted on.There is little reason to use the [ Package Model ] keyword unless intending to include RLGC matrices. The G (conductance) matrix is almost always zero. The R matrix is often zero, and when included, is almost always the self-resistance of the pin. The C & L matrices contain the mutual coupling elements that are the chief motivation for using the [ Package Model ].Required if [ Series Pin Mapping ] keyword used. This mapping covers only the series paths between pins. The package parasitics and any other elements such as additional capacitance or clamping circuitry are defined by the model_name that is referenced in the [Pin] keyword.

The model_names under the [Pin] keyword that are also referenced by the [Series Pin Mapping] keyword may include any legal model or reserved model except for Series and Series_switch models. Note 10: Required if [Series Switch Groups ] keyword used. Only one of ‘On’ or ‘Off’ is required since the undefined states are assumed to be the opposite of the explicitly defined states. The first line defines the default state of the series of switches.Note 13: Only keywords associated with Series_switch electrical models are permitted under [ On ] or [ Off ].  The Series electrical models describe the path for one state only and do not use the [ On ] and [ Off ] keywords. This series RLC model is defined to allow IBIS to model simple passive models and/or parasitics. The model is: »Usage Rules: A programmable buffer must have an individual [ Model ] section for each one of its modes used in the .ibs file. The names of these [ Model ]s must be unique and can be listed under the [ Model Selector ] keyword and/or pin list. The name of the [ Model Selector ] keyword must match the corresponding model name listed under the [ Pin ] or [ Series Pin Mapping ] keyword and must not contain more than 20 characters. A .ibs file must contain enough [ Model Selector ] keywords to cover all of the model selector names specified under the [ Pin ] and [ Series Pin Mapping ] keywords. The section under the [ Model Selector ] keyword must have two fields. The two fields must be separated by at least one space or tab character.

However, the use of tab characters is not recommended in general. The first field lists the [ Model ] name (up to 20 characters long). The second field contains a short description of the [ Model ] shown in the first field. The contents and format of this description is not standardized, however it shall be limited in length so that none of the descriptions exceed the 80-character length of the line that it started on. The purpose of the descriptions is to aid the user of the simulator tool in making intelligent buffer mode selections and it can be used by the simulator tool in a user interface dialog box as the basis of an interactive buffer selection mechanism. The first entry under the [ Model Selector ] keyword shall be considered the default by the simulator tool for all those pins that call this [ Model Selector ]. The operation of this selection mechanism implies that a group of pins that use the same programmable buffer (i.e. model selector name) will be switched together from one [ Model ] to another. Therefore, if two groups of pins, for example an address bus and a data bus, use the same programmable buffer, and the user must have the capability to configure them independently, one can use two [ Model Selector ] keywords with unique names and the same list of [ Model ] keywords. However, the usage of the [ Model Selector ] is not limited to these examples. Many other combinations are possible. »