Re: Can't do T-LINE?

Hi Chris,

 This is not an oversight and you can and should build
a distributed model if both L and C are present and it has
non-zero length it is suppose to be a distributed model.
Z0 = sqrt(L/C)
delay = sqrt(L*C)
The key is that the L and C are per unit length.
as is stated in the text. Just multiply the delay times
the length specified.

At 05:56 PM 5/19/98 -0700, Chris Rokusek wrote:
>( I am reposting this question in hopes of a more helpful response )
>Hi All,
>Concerning [Path Description] section in Ver 3.x of .ibs...
>The 'len' parameter is given in 'units' which is 'arbitrary' (i.e. not
>meters) such that a distributed T-LINE model cannot be built with the
>proper physical length.
>
>** I DO NOT WANT TO BUILD A LUMPED MODEL, I WANT TO BUILD A T-LINE MODEL
>**
>
>Is this an oversight or am I not understanding the parameters?
>
>Best Regards,
>
>Chris Rokusek
>Viewlogic Systems
>
>
>
>|==========================================================================
===
>| 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 Tue May 19 20:42:41 1998