length

Hi All,

I have a Question on the [Path Description] section in Ver 3.x of .ibs...

How do we convert the "Len"'s to physical lengths--what are the
"units" (meters?).

-Chris Rokusek
Viewlogic/MTS

|=============================================================================
| Keyword: [Path Description]
| Required: Yes
| Description: This keyword allows the user to describe the connection
| between the user accessible pins of a part and the pins of the
| ICs mounted on that part. Each pin to node connection is
| divided into one or more cascaded "sections", where each
| section is described in terms of it's L/R/C per unit length.
| The Fork and Endfork subparameters allow the path to branch to
| multiple nodes, or another pin. A path description is
| required for each pin whose signal name is not "GND", "POWER"
| or "NC".
|
| Board Description and IC Boundaries:
|
| In any system, each part interfaces with another part at some
| boundary. Every part model must contain the components
| necessary to represent the behavior of the part being modeled
| within its boundaries. The boundary definition depends upon
| the parts being represented by the model.
|
| For CARD EDGE CONNECTIONS such as a SIMM or a PC Daughter
| Card plugged into a SIMM Socket or Edge Connector, the
| boundary should be at the end of the board card edge pads as
| they emerge from the connector.
|
| For any THROUGH-HOLE MOUNTED PART, the boundary will be at the
| surface of the board on which the part is mounted.
|
| SURFACE MOUNTED PART models end at the outboard end of their
| recommended surface mount pads.
|
| If the board level component contains an UNMATED CONNECTOR,
| the unmated connector will be described in a separate file,
| with its boundaries being as described above for the
| through-hole or surface mounted part.
|
| Sub-Params: Len, L, R, C, Fork, Endfork, Pin, Node
| Usage Rules: Each individual connection path (user pin to node(s))
| description begins with the [Path Description] keyword and a
| path name, followed by the subparameters used to describe the
| path topology and the electrical characteristics of each
| section of the path. The path name must not exceed 40
| characters, blanks are not allowed, and each occurrence of the
| [Path Description] keyword must be followed by a unique path
| name. Every signal pin (pins other than POWER, GND or NC)
| must appear in one and only one path description per [Begin
| Board Description]/[End Board Description] pair. Pin names do
| not have to appear in the same order as listed in the [Pin
| List] table. The individual subparameters are broken up into
| those that describe the electrical properties of a section,
| and those that describe the topology of a path.
|
| Section Description Subparameters:
|
| The Len, L, R, and C subparameters specify the length, the
| series inductance and resistance and the capacitance to ground
| of each section in a path description.
|
| Len The physical length of a section. Lengths are given
| in terms of arbitrary 'units'. Any non-zero length
| requires that the parameters that follow must be
| interpreted as distributed elements by the simulator.
| L The series inductance of a section, in terms of
| 'inductance/unit length'. For example, if the total
| inductance of a section is 3.0 nH and the length of
| the section is 2 'units', the inductance would be
| listed as L = 1.5 nH (i.e. 3.0 / 2).
| C The capacitance to ground of a section, in terms of
| capacitance per unit length.
| R The series DC (ohmic) resistance of a section, in
| terms of ohms per unit length.
|
| Topology Description Subparameters:
|
| The Fork and Endfork subparameters denote branches from the
| main pin-to-node or pin-to-pin connection path. The Node
| subparameter is used to reference the pin of a component or
| board as defined in a .ibs or .ebd file. The Pin subparameter
| is used to indicate the point at which a path connects to a
| user visible pin.
|
| Fork This subparameter indicates that the sections
| following (up to the Endfork subparameter) are part
| of a branch off of the main connection path. This
| subparameter has no arguments.
| Endfork This subparameter indicates the end point of a branch.
| For every Fork subparameter there must be a
| corresponding Endfork subparameter. As with the Fork
| subparameter, the Endfork subparameter has no
| arguments.
| Node reference_designator.pin
| This subparameter is used when the connection path
| connects to a pin of another, externally defined part.
| The arguments of the Node subparameter indicate the
| pin and reference designator of the external
| component. The pin and reference designator portions
| of the argument are separated by a period ("."). The
| reference designator is mapped to an external
| component description (another .ebd file or .ibs file)
| by the [Reference Designator Map] Keyword. Note that
| a Node MUST reference a model of a passive or active
| component. A Node is not an arbitrary connection
| point between two elements or paths.
| Pin This subparameter is used to mark the point at which
| a path description connects to a user accessible pin.
| Every path description must contain at least one
| occurrence of the Pin subparameter. It may also
| contain the reserved word NC. The value of the Pin
| subparameter must be one of the pin names listed in
| the [Pin List] section.
|
| Using The Subparameters to Describe Paths:
|
| A section description begins with the Len subparameter and
| ends with the slash (/) character. The value of the Len, L,
| R, and C subparameters and the subparameter itself are
| separated by an equals sign (=); whitespace around the equals
| sign is optional. The Fork, Endfork, Node and Pin
| subparameters are placed between section descriptions (i.e.,
| between the concluding slash of one section and the 'Len'
| parameters that starts another). The arguments of the Pin and
| Node subparameter are separated by white space.
|
| Specifying a Len or L/R/C value of zero is allowed. If
| Len = 0 is specified, then the L/R/C values are the total for
| that section. If a non-zero length is specified, then the
| total L/R/C for a section is calculated by multiplying the
| value of the Len subparameter by the value of the L, R, or C
| subparameter. However, as noted below, if a non-zero length
| is specified, that section MUST be interpreted as distributed
| elements.
|
| Legal Subparameter Combinations for Section Descriptions:
|
| A) Len, and one or more of the L, R and C subparameters. If
| the Len subparameter is given as zero, then the L/R/C
| subparameters represent lumped elements. If the Len
| subparameter is non-zero, then the L/R/C subparameters
| represent distributed elements and both L and C must be
| specified, R is optional.
|
| B) The first subparameter following the [Path Description]
| keyword must be 'Pin', followed by one or more section
| descriptions. The path description can terminate in a Node,
| another pin or the reserved word, NC.
|
| Dealing With Series Elements:
|
| A discrete series R or L component can be included in a path
| description by defining a section with L=0 and the proper R or
| L value. A discrete series component can also be included in
| a path description by writing two back to back node statements
| that reference the same component (see the example below).
| Note that both ends of a discrete, two terminal component MUST
| be contained in a single [Path Description]. Connecting two
| separate [Path Description] with a series component is not
| allowed.
|-----------------------------------------------------------------------------
|
| An Example Path For a SIMM Module:
|
[Path Description] CAS_2
Pin J25
Len = 0.5 L=8.35n C=3.34p R=0.01 /
Node u21.15
Len = 0.5 L=8.35n C=3.34p R=0.01 /
Node u22.15
Len = 0.5 L=8.35n C=3.34p R=0.01 /
Node u23.15
|
| A Description Using The Fork and Endfork Subparameters:
|
[Path Description] PassThru1
Pin B5
Len = 0 L=2.0n /
Len = 2.1 L=6.0n C=2.0p /
 Fork
 Len = 1.0 L = 1.0n C= 2.0p /
 Node u23.15
 Endfork
Len = 1.0 L = 6.0n C=2.0p /
Pin A5
|
| A Description Including a Discrete Series Element:
|
[Path Description] sig1
Pin B27
Len = 0 L=1.6n /
Len = 1.5 L=6.0n C=2.0p /
Node R2.1
Node R2.2
Len = 0.25 L=6.0n C=2.0p /
Node U25.6
|
|=============================================================================
 
Received on Wed Sep 17 12:18:11 1997