Mast Language Reference Man

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MAST Language

Reference Manual

Release 2003.06, June 2003


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M AST L anguage Reference M anu al (J un e 2003) v

Copyright 1985-2003 Synopsys, I nc.

MAST Language Reference Manual

Cha pter 1. Overview .....................................................................................1-1

File for C lan gua ge declar a tions included.......................................1-3

A compound st a tement in a templat e ca nnot ha ve an empty body1-3

A foreign routine in a template th a t does not r eturn a va lue can causeerrors .................................................................................................1-3

You cannot use a n enumera ted ty pe para meter (enum) as an externalva ria ble in a templa t e ......................................................................1-3

Cha pter 2. MAST Sy nt a x Rules ...................................................................2-1

Cha pter 3. Declara t ions and Da ta Structures ............................................ 3-1

Cha pter 4. Expressions .................................................................................4-1

Cha pter 5. Int rinsic Functions a nd Va lues ................................................. 5-1

Cha pter 6. S ta tements ..................................................................................6-1

Cha pter 7. Templates ...................................................................................7-1

Cha pter 8. Foreign Fu nctions ......................................................................8-1

Cha pter 9. MAST Functions ........................................................................ 9-1

Index ......................................................................................................... In dex-1


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MAST L anguage Refer ence M anu al

vi M AST L anguage Reference M anu al (J un e 2003)



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M AST L anguage Reference M anu al (J un e 2003) 1-1


chapter1

Overview

Introduction

This ma nua l describes th e MAST modeling la ngua ge. This la ngua ge lets y oucr ea t e a m od el of a n y a n a log s ys tem or elem en t t h a t ca n be d efi n ed in t er ms of

nonlinear lumped a lgebraic or differentia l equa tions. Some extensions a re

a lso provided by th e use of ideal dela y a nd scheduling.

After completing a model, you ca n use it a s input t o the Sa ber simula tor. Youca n a l so u se t h e M AS T l a n gu a ge t o cr ea t e d ig it a l m od els t h a t t a k e on d is cr et eva lues a t discrete t imes. With t he MAST lan gua ge and th e Sa ber simulator,you ca n m odel an d simula te most physica l syst ems: electronic, mecha nica l,

optica l, hydr a ulic, etc. (or an y combina tion of them).

The MAST la ngua ge is a uniq ue concept in simula tor input th e sam ela ngua ge describes models of elements, of subsys tems, a nd of full systems. As ys t em m od el ca n be a s s im ple a s a n et lis t t h a t d es cr ibes t h e in t er con n ect ion sof existing s yst em components (using pre-defi ned models from a MAST

libra ry) or a s complex as t he full syst em description (using no pre-defi nedmodels).

At m inimum, the S a ber simula tor requires (for each syst em to be simulat ed)a n input fi le conta ining a n etlist tha t completely describes the system in t heMAST la ngua ge.

NOTE

Th e simul ator al so accept s files conta i ni ng SPICEin put , after th ey have been conver ted t o MAST formatwi th thespitosconver si on u ti l i ty. However, the Sabersim ul ator is in her ent ly compati ble wi th th e M ASTlanguage, so using M AST models prov ides both greatermodel i ng flexi bi l i ty an d better sim u l at i on speed.


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Chapter 1: Overview

1-4 M AST L anguage Reference M anu al (J un e 2003)


Templates and Hierarchy

A complete MAST description of a n element, s ubsyst em, or entire sy stem isconta ined in a fi le a nd is ca lled a t empla te.

The MAST lan guage supports designs, w hich m eans tha t templates cancont a in references to oth er templa tes. If one templa te (sa y t emplat e A)

con t a in s a r ef er en ce t o a n ot h er (t em pla t e B ), t h is in dica t es t h a t , in t h e m od el,the syst em represent ed by templat e B is a subsystem of tha t represented bytemplate A. You ca n crea te a t emplat e tha t defi nes a subsyst em, and t henrefer t o it in t he syst em template w herever t he subsystem is used. When yout a k e f ull a d v a n ta g e of h ier a r ch ica l m od elin g, t h e m os t n a t u ra l s t ru ct u re of t h e

model is th e structur e of the syst em it models.

A reference in one templa te to a nother templat e is a netlist entr y. U singnetlist entries to defi ne a syst em hiera rchica lly ca n signifi ca ntly increase the

speed of simulat ion.

The MAST la ngua ge pla ces no restrictions on th e depth of th e templat eh iera rchy. Moreover, any level may cont a in any number of references to lowerlevels, and ca lled templa tes can be defi ned either insid e or outside of the

ca lling templat e.

B eca use we supply substa ntia l librar ies of sta nda rd component a nd elementtempla tes, you ca n usua lly simplify your model-w ritin g effort by in cludingreferences, w henever possible, to these templa tes. In m a ny ca ses, you candefi ne an entire system using only netlist entries th a t call libra ry templat es.Such a sy stem is ca lled a netlist .

A netlist entr y is equiva lent to th e full defi nition of the referenced template.For example, a net l is t reference to a predefi ned res is tor t empla te i s equ iva len tto a full defi nit ion of tha t r esistor. Moreover, th e netlist r eference wouldspecify th e value of the resistor (in ohms), a nd t ha t value w ould be passed tothe r esistor templat e.

If a templa te consist s only of a full model description inst ead of referencing

oth er templat es, it is ca lled fl a t . Fla t descriptions ha ve two disadva nta ges:

In most cases, s imula t ion requires more t ime.

I f t h er e a r e m ult iple occu rr en ces of a s ubs ys tem , it s d escr ipt ion m us t bew rit ten in full for ea ch occurr ence, reducing simula tion effi ciency an dincrea sing th e size of th e input fi le.

Naming the Template File


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Templ ate Or gani zati on


Copyright 1985-2003 Synopsys, Inc.

You ca n use your syst ems editor to crea te a templa te fi le in t he MAST

lan gua ge. Give it a na me of this form:

templatename.sin

wheretemplatename

is t h e n a m e of y ou r t em pla t e, w h ich ca n m od el a s ys tem ,subsys tem, or component . The number of cha rac ter s a l lowed in templatenamedepends upon your opera t ing system. The .sin ex tens ion is requ ired for use byth e Sa ber simula tor. The templatenamemust sta rt w ith a lett er. The othercha ra cters in t he na me ma y be lett ers, numbers, or und erscores. If you ha vea n input fi le previously creat ed in the SP IC E forma t, you ca n convert it t oSa ber forma t w ith th e Spice-to-MAST Tra nsla tion t ool nspitos. For adescription of the n spitos tool, refer t o nspitos in th e SaberBook Onl in e H elpSystem.

The top-level templa te in a hiera rchica l syst em model conta ins othertemplates or references to them, a nd is not referred to by other t emplat es.

When invoking the Sa ber s imula t or, you ca l l the top-level templa te direct ly, asfollow s, wh ere brackets ([ ]) denote optiona l items:

saber [opt ions] templ atename[.sin]

Template Organization

This section presents an overview of template organization.

Templa tes have a genera l form consis t ing of severa l di fferent sect ions . You usesome or a ll of t he possible sections depending on th e requirement s of yourmodel a nd w hether y ou include previously defi ned t empla tes in your model.

Wit h in y ou r t em pla t e, a t a n y poin t , y ou ca n s pecif y ot h er fi l es, t h e con t en t s of

w hich a re read int o the templa te. Included fi les a re ca lled include fi les.I n clu de fi l es ca n con t a in pa r t , or ev en a l l, of a t em pla t e. Th e pos sible t em pla t esections a re as follow s:

Unit definitions

Connection point definitions

Template header

Header declarations

{

Local declarations

Parameters section

Netlist section

When statements

Values section


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Control section

Equations section

}

In genera l, the more complicat ed th e model, the more templat e sections you

w ill probably use.

In a h iera rchica l syst em model, the top-level templa te models the wh oles ys t em a n d ca n con t a in t em pla t es t h a t d efi n e t h e s ubs ys t em a n d com pon en t s.Templa tes wi th in the top level t empla te can ei ther be expl ici t ly defi ned wi th in

t h e t em pla t e fi l e, or ca n be d efi n e d in s epa r a t e fi l es a n d in clu ded by r efer en ce.

The top level templat e must not conta in a templat e header, th e headerdecla ra tions section, or the bra ces ({ }) surr ounding t he body of thetemplate. When you invoke the Sa ber simulator to a na lyze a sy stem model,you use the na me of th e fi le conta ining th e top level templat e in the S a berinvoca tion line.

When wr iting templates, you should bear in mind t w o importa nt r ules th a t

a ffect t he positions of relat ed items.

1. You m us t a l wa y s d efi n e s om et h in g befor e y ou u se it . For exa m ple, if t h etemplat e uses a va riable, tha t va riable must be declared prior to itsfi rs t occur rence. The exception is th e use of implicitly decla redpins

a nd s ome forw a rd r eferences to component svars. S imvars a ndintrinsic functions are also implicitly declared.

2. Wh er e y ou d efi n e s om et h in g d et er m in es w h et h er it is d efi n e d loca l ly orgloba lly. In pa rt icula r, if you include or defi ne a templa te before a

templat e header, it is a ccessible by a ll templa tes below th a t one in thetempla te hiera rchy. This is genera lly tru e for other decla ra tions.H owever, if you defi ne it a fter t he hea der decla ra tions section (forexam ple, in th e local decla ra tions section) then it is visible only in t he

local scope. Loca l scope means th a t the pa rticular defi nition isa cces sible on ly t o t h a t t em pla t e a n d pos sib ly t o it s d es cen d a n ts. (O t hertemplat es ca n include or defi ne th e sam e thing independently.)

As lon g a s y ou com ply w it h t h es e r ules, t em pla t e s ect ion s d o n ot h a ve t o be ina part icular order.

Unit and Connection Point Definitions

The~ unit defi nition specifi es the units for certa in va riables such a s th roughva riables, across va riables,vars,refs,states, andvals. Unit definit ionsset t he id en tifi er used t o in dica t e t he un it s of a n um ber t ha t w ill r esult fr om acalculation.


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The connect ion point defi nit ion specifies the connect ion point s a templa te can

use. If they a re pin-type, it implies t he na mes of the th rough an d a crossva riables, tw o importa nt va riables associat ed with a ll pins.

The connection point d efi nit ion is importa nt beca use it tells th e Sa bersimulat or w hich va riable to solve for a nd w hich must be equa l to zero at a

connection point. I n a ddition, it a llow s th e simulator to ma ke sure tha t onlycompa tible components a re conn ected.

B eca use the connection point defi nition uses units, it must follow the un it

defi nition in th e templat e.

St a nda rd unit a nd connection point defi nitions appea r inunits.sin, w hichis included in the fi le header.sin. If you invoke th e Saber simulat or w ith t he-laoption, header.sinis aut omat ica lly loa ded. If you wish, you may cha ngeunits.sina nd r e-compile it u sing t hesaber -poption.

Header

The header for a t emplat e fi le defi nes the na me of the templat e, the na mes ofits connection points, a nd the n a mes of the templates a rguments used in anetlist entry. You must include the header in a ny t empla te th a t y ou w ill ca llfrom a nother templat e; tha t is, a ny t emplat e except a top level template.

The hea der includes the na me of th e templat e, th e na mes of the connectionpoints, an d a ny a rguments a ssociat ed with it . Whenever you defi ne a

pa r t icu la r elem en t by r efer rin g t o it in t er ms of t h e t em pla t e t h a t d efi n es it (anetlist sta tement), the form a nd content of the header sta tement defi nes theform of th e netlist sta tement.

Declarations

There are tw o sections tha t cont a in declara tions: hea der declara tions an dlocal decla ra tions. All na mes (identifi ers) must be defi ned before th ey ca n be

used. These defi nitions ar e ca lled declara tions. Keyw ords (names t ha t a rerequired pa rt of MAST sta tements) a re defi ned by the langua ge and requiren o f ur t her d ecla r a t i on . A d ecla r a t ion t ells t h e s ys t em t h e t y pe t o be a s socia t edw ith t he na me, th us defin ing how it is to be used. Some declar a tions ca n a lsoinclude the assignment of an initial va lue.

The purpose of head er decla ra tions is to defi ne to the syst em th e na mes used

in t he head er. The loca l declara tions defi ne th e na mes used in t he rest of thetemplateit cont a ins declara tions for a ll ident ifi ers used inside th e templa te.

Th e n a m e of t h e t em pla t e d oes n ot r eq uir e a s epa r a t e d ecla r a t ion ; in fa ct , t h eheader it self is th e declara tion of th e template na me. The other na mes use inthe header (names of connection points and arguments) must be declared inthe hea der declara tions.


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Declara tions of connection points must defi ne th eir t ype (pin,ref,var, orstate). Declara tions of a rguments defi ne the ty pe of each argum ent.Argum ent ty pes fall int o one of thr ee ca tegories: simple, composite, or a rra ysof sim ple/composi t e.

U ndersta nding declar a tions is a key to understa nding how to use the MAST

lan gua ge and is explained in more deta il in th e cha pter on Decla ra tions andDa ta S t ructures .


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The Parameters Section

The P a ra meters section is used to ma nipula te par a meters. You can use it t oa dd error checking to templa tes by t esting th e input va lues of argument s forva lidity a nd to model sta tistical distributions for Monte Ca rlo a na lyses.

Pa ra meters an d ar guments a re similar. They ca n ha ve the sa me types ofdeclara tions, but par a meters ar e declared loca lly in a t emplat e, wh ilea rguments a re declared in th e hea der declara tions section and their va lues

ca n be passed into a t emplat e by using a netlist st a tement. H ow ever, onlya r g um en t s a n d in it ia l iz ed pa r a m et er s ca n be ch a n ged by t h ealter commandin the Sa ber simulat or. Only para meters may be cha nged in the Pa ra meterssection.

The sta tements in t he Pa ra meters section are evalua ted a s follow s:

O nce ju st a f t er t h e in pu t fi l e is r ea d

E a ch t im e t he S a beraltercomma nd is used (ca using a tempora rya lterat ion of a t emplate a rgument)

For each run of a Monte C a r lo s imula t ion

Pa ra meters may depend only upon other para meters, a rguments a ndconstants.

Assignment st a tements, expressions, an d conditional st a tements (if-else)a re allowed in th is section. Mat hema tical expressions a nd int rinsic functions

a re allowed in t his section w ith t he exception ofd_by_dt(x)(th e deriva tivefunction) and thedelayfunction. Calls to foreign subroutines are allowed.

The Netlist Section

The Netlist section consists of one ore more netlist sta tement s th a t ca ll oth ert em pla t es. Th es e s t a t em en t s d efi n e elem en t s of t h e s ys t em t h a t a r e in st a n cesof the t emplat e(s) being called. The Netlist section is r equired only in

templates t ha t ma ke reference to other t emplat es; in fact , it is a nimplementa tion of anoth er level of hiera rchy.

The form of a netlist st a tement is a s follow s:

templatename.refdes connect ion_pt_l i s t [= argument_assignments]

The templatenameis t h e n a me of t h e t em pla t e y ou a r e ca llin g, a s id en t ifi e d inits header.

The refdesis th e reference designat or, a unique na me for t ha t element of thesystem.


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Conditiona l stat ements a re allow ed in this section, a s well a s mat hema tical

expressions a nd in tr insic functions, except for t hed_by_dt,delaya ndrandom()intrinsic functions. Foreign subroutines are also allowed.

Control Section

The Cont rol section decla res specifi c informa tion to th e simulat or tha t doesnot fi t in oth er sections of th e templat eit is not req uired in a ll models. Theinforma tion th a t th e Control section provides is specifi c to the sy stem being

analyzed.

The Cont rol section can cont a in th e follow ing ty pes of sta tement s:

Condi t iona l s t a t ements tha t can col lapse two nodes into a s ing le node,thereby speeding up the s imula t ion . However, once nodes a re coll apsedduring a s imula t ion , you cannot undo i t w i thou t exi t ing and re-enter ingth e Saber simulat or.

S ta tements tha t declare groupings of nonl inear va lues for the purposeof piecew ise linear evalua tion, defin ing t he independent va riables foreach group

S ta tements tha t declare the sample points for each independentva ria ble used in t he piece-w ise linea r set

S ta tements tha t declare Newton s teps for the specified independentvariables

S ta tements tha t descr ibe smal l-s igna l noise sources

Ea ch of these sta tements is described in th e Templatessection.

Equations Section

The Equa t ions sect ion descr ibes the ana log cha rac ter is t ics a t the termina ls oft h e elem en t t h e t em pla t e is d efi n i n g. I n ef fect , t h is s ect ion d efi n e s t h e effect ofthe element on t he rest of the system.

St a tements in th e Eq ua tions section indicate the relationship of the ana log

cha rac ter is t ics of specia l va r iab les to va r iab les in the res t of the system. Thesesta tements use t he special opera tors+=(is a dded t o) a nd-=(is subtr a ctedfrom) to indicate t his relat ionship. Mat hema tical expressions a nd int rinsic

functions a re a llow ed in th is section. The int rinsic functionsd_by_dta nddelaya re allowed a s w ell, but ma y not be nested. Therandom()function isnot a llow ed.


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Miscellaneous

Include Files

There are t w o way s to bring the cont ents of oth er fi les into a templat e. One

wa y is with the net l ist sta tement , w hich refers to a t emplate a nd defin es theconnections of its t erminals t o nodes of th e system. The other wa y is w ith th einclude sta tement, w hich ha s th e follow ing form:


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Miscellaneous



Template Variables

Several different t ypes of var iables ca n be used in a template. Ea ch t ype hasits ow n fun ction a nd us es. The ty pes of va ria bles are listed below.

U ndersta nding th e concepts behind t hese var iables is essentia l for a nyt hingbut th e most rudimenta ry t emplate usa ge.

S yst em va ria bles- th rough va riables- a cross va ria bles- vars- refs

S im ula t or va r ia bles

P a ra met ers

Arguments

Va lues (vals)

states

Th e t a sk of a s im ula t or is t o d es cr ibe t h e beh a vior of a m a t hem a t ica l m od el ofa physica l system. For t he Sa ber simula tor, the model is a system ofsimulta neous (linea r or nonlinear ) a lgebraic an d ordinar y differentia l

equa tions, or both .

Th e pu rpos e of t h e M AS T l a n gu a ge is t o s pecify t h e m od el of t h e s ys tem t o besimula ted. The lan gua ge must be a ble to do th e follow ing:

1. Allow arguments to be passed into templat es.

2. Specify how t he templa te is connected to the rest of the system. Morespecifi ca l ly, th i s means specifying the interact ions of element s in termsof the equat ions tha t a rise from physica l law s when entit ies are

con n ect ed (a t n od es ) t o for m a s ys t em . I n elect r ica l s ys t em s, t h es e la w sa r e K ir ch off s cu rr en t a n d v olt a g e la w s (K C L a n d K VL ). Th es e t w o la w sma y be sta ted, respectively, a s th e sum of the currents leaving a nodeis zero and th e sum of volta ge drops a cross elements in a ny loop iszero.

3. Specify the equa t ions th at describe the a na log behavior of the system.For example, the equations describing the analog behavior of a resistora rev=i*ra nd th ose for a ca pacitor a rei=c*dv/dt, wh ere, in bothcases,va ndiar e the volta ge across an d the current t hrough theelement, respectively.


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Chapter 1: Overview



4. Specify the discrete behavior of the syst em. You can use When

sta tements t o tell the simula tor how t o schedule discrete events a ndtime steps.

5. Allow fl exibility in specifying system beha vior.

6. K eep t h e s im ula t ion a s fa s t a s poss ible by s epa r a t in g v a ria bles in t o t h efollowing:

a . Those tha t must be evalua ted cont inuously

b. Those that must be evalua ted on a n event-driven basis

c. Those tha t can be eva luat ed only a s needed or for post-processing

d. Those tha t have to be evaluat ed only once for each simulat ion

To fulfi ll th ese var ious fun ctions, t he MAST la ngua ge offers t hese differentty pes of va ria bles, each of wh ich is d escribed in t he follow ing section.

System Variables

Syst em var iables are t he va riables for w hich t he simulat or solves. Theyinclude across variables,vars, an drefs. You cann ot a ssign va lues t o these

va riables in a t empla te. Only the simulat or ca n a ssign their values.

To genera l ize KC L and KVL so they apply to both elect r ica l and non-elect r ica lsystems, tw o associat ed qua nt it ies must be defi ned for each connection point:the throughand the acrossva riables. The rule for t hrough va riables is a sfollows:

The sum of all t hrough va ria bles lea ving a node is zero.The rule for across va ria bles is as follow s:

The sum of all a cross va ria ble differences ar ound a ny closed pat h iszero.

Across and through variables for various technologies are as follows:

Through Across

Electrical current volt a ge

Rotational t orque a ngula r velocit y

Mechanical force posit ion

Fluid fl ow ra te pressure

Thermal pow er tempera t ure


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Miscellaneous



Modified Nodal Analysis

The supplied t empla tes usua lly use a m odifi ed nodal a na lysis technique. Innodal a na lysis , through varia bles are added to a nd subtra cted from t hesystem m a trix directly, an d t hen th e simulator solves for a cross varia bles.Therefore, through var iab les a re dependent va r iab les and across va r iab les a re

independent va riables. In ma ny cases, how ever, nodal a na lysis must bemodifi ed . For example, modifi ca t ion is requ ired where ac ross va r iab les a re not

f un ct ion s of t h rou gh v a r ia b les, s uch a s in a n id ea l v olt a g e s ou rce, in w h ich t h ecurrent is w ha tever it needs to be to give th e defi ned volta ge. In such a ca set h e t h r ou gh v a r ia b le, cu rr en t , is a n in d epen d en t v a r ia b le, w h ich is h a n d led b ya dding a n equa tion to th e system of equa tions.

In general, most through varia bles ar e dependent va ria bles an d all a crossvariables are independent variables. These variables are declared implicitly

through the pin decla r a t ions. For example, when you defi ne a connect ion pointx t o be elect r ica l , t he s imula tor au toma t ica l ly crea tes an independent va r iab le

of the formv(x)a nd th e dependent va riablei(x).

An independent t hrough var iable, such a s the current th rough a voltagesource, must be decla red a s avarin t he loca l declara tions section. It must bea ssocia ted wit h a n equa tion in the Equa tions section of the form:

var: expression= expression

Avaris not decla red in t he formi(x)(for example, as a current a t a pin),beca u se t h a t for m w ou ld d en ot e a d epen den t va r ia b le. You ca n a ls o u se avarfor situa tions tha t a rise less frequently. In cases w here you need to ta ke

multiple derivat ives a nd delays (which cann ot be nested), you can declare avar.

You ca n a lso defi ne avara s a n independent varia ble tha t can be passeda nother template, in wh ich it is declar ed aref.

In general, the dependent var iable in a t emplat e is the through varia bledefi ned in rela tion to a conn ection point . The independent va ria bles in a

template a re a cross varia bles defi ned in relat ion t o a connection point,varstha t a re associated w ith a n a ddit iona l equa t ion in the E qua t ions sect ion, andoccasionally asrefs.

Dependent t hrough va riables an d independent a cross va ria bles a re declaredimplicitly by thepindeclar a tions. They a re associat ed with equat ions in t heEq ua tions section using the following forma ts:

through(pin) += expression

through(pin) -= expression

through(pin1->pin2) += expression


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Chapter 1: Overview



The formthrough(p in1->pin2) -= expressionis a lso possible, but is lessreada ble a nd is not r ecommended.

Avarmust be declar ed in the loca l declar a tions section a nd m ust bea s socia t ed w it h a n eq ua t ion in t h e E q ua t ion s s ect ion , w h er e t h e eq ua t ion h a sthe formvar: expression = expression. A ref must be ident ifi ed , a long

w i t h ot h er con n ect ion poin t s, in t h e t em pla t e h ea d er, a n d m us t be d ecla r ed inth e header declara tion section. For exam ples, refer t o th e Templatessection.

Simulator Variables

Simula tor var iables (simvar s) a re varia bles used by the simulat ion. They a renot directly pa rt of th e system of equa tions tha t d escribe the model, but ma ybe used in va rious w ay s th roughout t he template. They a re used mostfrequently in conditiona l sta tements (if-else). Simva rs include th efollowing:

The simulat or a ssigns va lues to most simva rs a ccording t o its own rules andrequirements. Exceptions a renext_timea ndstep_size, which give

informa tion to the simula tor. A templa te need not provide values t o th esesimvar s. However, if a template does provide a va lue, th e simulator uses th eva lue to infl uence its choice of th e next t ime step or time-step size in t hesimulation.

The simulat or a utomat ica lly declar es simvar s, so you n eed n ot declar e them.However, if you declare a var iable with t he same na me as a simvar (not

recommen ded), then y our decla ra tion overrides t he a utoma tic one, so youcan not use that varia ble as a simvar.

You ca n use simva rs in When st a tements a nd in th e Va lues section, an d incer t a in ci rcumstances , in the Equa t ions sect ion . The s t a t i st i ca l s imvar can be

used in the Pa ra meters section an d in th e Netlist section.

Arguments

Ar gu men t s a r e n a m ed in t h e t em pla t e h ea d er, a n d v a lu es for t h em a r e pa s sedinto a t empla te via a netlist entry. You declare each a rgument in the hea derdecla ra tions sectioneither a s one of th e thr ee simple types, a s one of th reecomposite ty pes, or a s a n a rra y of simple a nd/or composite ty pes.

dc_domain freq next_time time_domain

dc_done freq_domain statistical time_init

dc_init freq_mag step_size time_step_done

dc_start freq_phase time tr_done

tr_start


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Miscellaneous



Arguments ca n receive their values in tw o way s:

1. B eing ini t ia l ized in the declara t ion

2. Ha ving values passed in through the ar gument l ist in a net l ist entry

A va lue passed in through a net l is t en t ry supersedes any ini t ia l ized va lue. You

ca n ch a n ge t h e v a lu e of a n a r gu men t d ur in g a s im ula t ion r un u sin g t h ealtercommand of the simulator.

Parameters

P a r a m et er s a r e v a ria b les u sed in expr es sion s t h a t a s sig n v a lu es t o ot h er t y pes

of va riables. Pa ra meters ca n be declar ed to be a ny of thr ee simple or t hreecomposite types, or a rra ys or combina tions th ereof. Pa ra meters a nda r g um en t s h a ve t h e s a m e t y pes of d ecla r a t i on s. You d ecla r e pa r a m et er s in t h elocal decla ra tions section.

A para meter can receive its va lue in t w o wa ys. You can either initialize it inthe declara tion or you ca n a ssign it a va lue in the Pa ra meters section, by

eith er an a ssignment st a tement or a foreign subroutine call. You can cha ngethis initia l value while runn ing the Sa ber simulat or, using th ealter

command.

Within t he Pa ra meters section, only para meters ca n a ppear on the left ha ndside of an a ssignment st a tement, or be returned from a foreign subroutineca l l. You ca n u se pa r a m et er s t o in it ia l iz e s t a t es. P a r a m et er s ca n be u sed in a l l

oth er sections in t he body of a templat e: the Pa ra meters section, Netlistsection, When st a tement s, the Va lues section, th e Contr ol section, an d th eEq ua tions section.

Vals

Vals are var iables tha t hold tempora ry informa tion during simulat ion, an dw hich can supply informa tion not otherwise a va ilable during post-simulat ion

processing.

Vals ca n r eceiv e t h eir v a lu es on ly in t h e Va l ues s ect ion of t h e t em pla t e: eit h erin an a ssignment sta tement (with t hevalon the left-ha nd s ide of th estatement) or as the return value of a foreign subroutine call. You mustdeclarevals in t he local declara tions a rea of th e template. You can use them

in t he Va lues section, the E qua tions section, an d in When st a tements.


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Chapter 1: Overview



States

States a re varia bles tha t hold informa tion pertinent t o discrete t imesimulation.Stateva riables ma y be digita l (discrete in va lues a nd d iscretein t ime), or event-driven a na log (cont inuous in va lues an d discrete in tim e).

States can receive their va lues in tw o way s:

1. U se astatea s a connection point in the hea der of a templat e, thenpass t he value in from a netlist .

2. Assign t hestate a va lue in a Wh en st a tem en t, w her e t he st a te ca n be

th e left-ha nd t erm of an a ssignment sta tement, can be used in var iousscheduling sta tements, or can ha ve its va lue return ed by foreignsubroutine calls.

I f astate is pa s sed in a s a con nect ion poin t , it m us t be d ecla r ed in t h e h ea d erdeclaration section; otherwise, it must be declared in the local declaration

section. You can usestates in When sta tements a nd in th e Va lues a ndEq ua tions sections.


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chapter2

MAST Syntax Rules

The genera l synt a x rules an d reserved w ords for t he MAST modelinglanguage are divided into the following topics:

Ident ifiers and Str ings

White Spa ce Usa ge

Netlist St a t ementComments

Line Cont inua tion

Section K eywords

Expressing R eal Num bers

MAST Keyw ords

MAST - Non-Reserv ed K eyw ords

Identifiers and Strings

Identifi ers a re na mes for va ria bles, templa tes, nodes, etc. There ar e tw o validforms for ident ifi ers. One must sta rt w ith a n a lpha betic cha ra cter or an

und erscore (_), followed by a lpha betic cha ra cters, digits, or und erscores. Theother form must sta r t w ith the@cha ra cter a nd be follow ed by a stringcon st a n t . Th er e is n o lim it on t h e n um ber of ch a r a ct er s in a n id en t ifi e r, a n d a l lcha ra cters a re signifi cant . B eca use the MAST lan guage is n ot ca se-sensitive,the follow ing w ords all refer t o the sam e ident ifi er:name,NAME,NaMe.

Ident ifi er s for connect ion point pins names can be unsigned integers, but onlyin netlist entr ies, and nowhere else in the templat e.

S t r ing cons t an t s cons is t of zero or more charac ter s, w i thou t any double quotesor newlines, enclosed in double quotes. Em pty st rings ca n be specifi ed as"".


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Chapter 2: MAST Syntax Rules



St ring consta nt s ca nnot span more th a n one line, alth ough you ca n use

conca tena tion a s follow s:

There a re no escape sequences (such as the C language backsla sh) ava i lab le ins t rin g con st a n t s. B y u sin g a for eig n s ubr ou t in e, y ou m a y en t er a d ou ble q u ot eor a new line into a st ring (refer t o Messa ges on page 5-10).

White Space Usage

B lan ks, ta bs, and comments (described la ter) are considered wh ite space,a nd a re ignored except t o separa te w ords w hen no oth er punctua tion isr eq u ir ed . F or exa m ple, bla n ks (s pa ces ) a ct a s s epa r a t or s in a lis t of n od es on atempla te reference.

Netlist Statement

A netlist st a tement (or t emplat e reference) is a netlist entr y in the n etlist

s ect ion of a t em pla t e t h a t ca l ls (r ef er s t o) a n ot h er t em pla t e. I t con sis t s of t h en a m e of t h e t em pla t e, f ollow ed by a per iod , follow ed by a r ef er en ce d es ig na t oras follows:

templatename.r efd es connecti on_poin ts [= argument_assignments]

The templatename.refdesis considered a complete unit, so no blanks a re

a llow ed wit hin it . The reference designat or (refdes) may consist of a lpha beticcha ra cters, digits, and underscores, w ith no requirement th a t t he fir stcha ra cter be a lphabetic.

The connection_pointscon sis ts of t h e n a mes of t h e n od es t o w h ich t h e m od elsconnection points a re joined. Ent ries in this list must be separa ted by w hitespace. The node nam es must either be in the sa me order an d qua ntit y a s theconn ection point s specifi ed in th e ca lled templat e, or they m ust be specifi edwith reference to the actual connection point names, in the form:

connection_point_name:node_name

"This is a long string. Because it might not"//

"fit on one line, it is put together using"//

"concatenation."


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I denti fiers and Str in gs



For exa mple, if th e diode (w ith th e reference designa tordx) is conn ect ed t o

nodes na mednode1a ndnode2, you can specify it eith er a s:

d.dx node1 node2

or as eith er of th e follow ing:

d.dx p:node1 n:node2

d.dx n:node2 p:node1

Also, node nam es ca nnot ha ve a number a s the fi rst cha ra cter unless allremaining characters are numbers:

Correct: 5,v16,vcc94b,6431

Incorrect: 5v,+5V,15v1

Non-a lpha num eric cha ra cters (such as + or -) a re not allowed.

The argument_assignmentsar e required only for templates th a t ha veuninitia lized ar guments. Forma ts for this a rgument list depend on th e datastructure of the ar guments. Multiple entries in a n a rgument list must besepa ra ted by comma s.

Comments

The MAST la ngua ge ignores blank lin es a nd comment s. A comm ent m ustbeg in w it h a pou nd s ig n (#) a n d is r ecogn iz ed a s r un nin g t o t h e en d of t h e lin e.

A comment ca n st a rt a nyw here within a line, wh ich is useful for tempora rilyremoving a line or pa rt of a line.

Line Continuation

Norma lly, a car riage return termina tes a line. A backsla sh (\) a t t he end of aline with no comment indica tes continua tion of th e line a nd is ca lled acontinua tion cha ra cter. It h a s no meaning in a n input fi le except t o indicate

continua tion, and if it is th e last non-comment cha ra cter on a line, it isdiscarded.

I n a d dit ion , ea ch of t h e follow in g in dica t es t h a t t h e lin e is t o be con t in ued if itis in cont ext (part of th e line) a nd it is th e last non-comment cha ra cter on t he

line:

+ - * /

& | < >

( { [ ~

, . : =


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The s emicolon (;) is a llow ed as a n explicit line termin a tor, but it is not

r eq u ir ed . Ty pica l ly a s em icolon is u sed t o a l low m or e t h a n on e s t a t em en t on as ing le l ine. One use for the semicolon is in da t a s t ructure defi nit ions, followinga lis t of v a ria bles, t o a llow t h e clos in g br a ce (} ) t o be on t he sa me lin e ra t hertha n t he follow ing line.

The line pa rser does not count th e pa rent heses in a line, an d so ca nn otdetermine whether a closing grouping symbol (),},]) is the fi na l one in a

sta tement . Therefore, in t he a bsence of th e line continua tion char a cter, aclosing symbol indica tes t he end of a line.

Section Keywords

The lef t b race ( { ) t h a t follow s a sect ion key w or d m us t a lw a y s be on t h e s a meline, right a fter t he keyword. These keyw ords a recontrol_section,equations,parameters, andvalues. The left bra ce must a lso directly

followwhen.

Expressing Real Numbers

All r ea l n um ber s ca n be expr es sed eit h er in t h e u su a l s cien t ifi c n ot a t ion , w i t hth e lett ers e or d expressing pow ers of 10, or w ith t he follow ing suffi xes:

You ca n express a number a s a const a nt immediately follow ed by a na ppropria te a bbreviat ion (do not include units).

No a lphanum eric cha ra cter ca n a ppear immediat ely a fter a suffi x; a spa ce orpunctua tion is required.

Note tha tmmea ns 10 , a ndmea ndmegmea n 10 .

a a t t o 10

f femto 10

p pico 10

n na no 10

u (or mu) micro 10

m milli 10

k kilo 10

meg (or me) mega 10

g giga 10

t t era 10

-18

-15

-12

-9

-6

-3

3

6

9

12

-3 6


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MAST - Non-Reser ved K eywords



For example, the following are equivalent:

x=3p x=3d-12 x=3e-12

The follow ing a re illega l specifi cat ions for nu mbers:

x = 3 p

(space not a llow ed betw een n umber an d a bbreviat ion)

x = 1mA

(units not a llow ed)

MAST Keywords

The follow ing keyw ords a re reserved in the MAST la ngua ge an d cann ot beused a s varia ble names in a template :

*Section keywords that must be followed by a left brace,{, on the same line.

MAST - Non-Reserved Keywords

Th e f ollow i ng g rou ps of key w or ds a r e n ot r es er ved a n d ca n be u sed a s v a r ia b lena mes, a lthough it is good practice to treat th em as if th ey were reserved:

Control Section Words

Simula tor Va riables

Int rinsic Functions

P redefi ned Numbers in hea der.sin File

component cont rol_sect ion* element else

enum equa t ions* ext erna l foreign

group if inf number

pa ra meters* pin ref ret urn

simva r st a t e st a t es st r ing

st ruc templa te undef union

unit va l va lues va r


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MAST - Non-Reser ved K eywords



Predefined Numbers in header.sin File

The following are predefined numbers in theheader.sinfi le:

Number Definition Description

temp = 27 Temperat ure va lue

mos_scale = 1.0 Sca le factor for mosfet physica l dimensions(used bym.sina ndspm.sin)

mos_scalm = 1.0 P rocess sca le factor for mosfet phys ica ldimensions (used bym.sinonly)

r_tol = 0 Resistor va lue tolera nce(f or exa m ple, a v a lu e of 0.05 in d ica t es a 5%tolerance resistor)

c_tol = 0 Ca pacitor va lue tolera nce(f or exa m ple, a v a lu e of 0.05 in d ica t es a 5%tolerance capacitor)

l_tol = 0 Ind uctor va lue toleran ce(f or exa m ple, a v a lu e of 0.1 in d ica t es a 10%tolerance inductor)

r_pdmax = undef Maximum power dissipation for resistor

(for exa mple, 1/4 W resis tors)

c_vmax = undef Forw a rd volta ge rat ing for capacitors

c_vrmax = c_vmax Reverse volta ge ra ting for capa citors(different fromc_vmaxfor electrolytics)

include_stress = 1 Allows remova l of stress an a lysis innetlisted templat es. Default va lue = 1 w ill

run str ess.

use_2g6 = 0 Allows invoca t ion of SP ICE 2G.6 compat ibleMOS m odels throughm.sina ndspm.sin

acc_fac = 1 Accuracy factor

G lobal va lues for hyd ra ulics library

rho = 1k G lobal va lue of r ho (kg/m**3)

mu = 14.3m G loba l va lue of mu (N-s/m**2)

bulk = 689.5meg G lobal v a lue of bulk m odulus (N/m**2)


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Loga rith ms a re expressed in MAST a s follow s:

base e = ln

base 10 = log

This differs from how other progra mmin g la ngua ges (such a s FOR TRAN,RATFOR , an d C ) express logarit hm s:

base e = log

base 10 = log10

patm = -101325 G lobal v a lue of pat m (N/m**2)

pcav = -95k G lobal va lue of pca v (N/m**2)

valid_pres = inf Stress ra t ing pa ram eter

Number Definition Description


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Chapter 3: Declar ati ons and D ata Str uctur es



decla r a t ion causes an impl ici t decla r a t ion of the associa t ed through and

a cross va ria bles. You must declarevars andrefs a nd specify th eirunits.

Val d eclar ati onsdecla re va ria bles and s pecify th eir unit t ypes. Thesimulat or a ssigns va lues t ovals only wh en needed, which is notnecessarily a t each time or frequency step.

Vals ca n a ct a s in t er m ed ia t e v a r ia b les t h a t r eceiv e v a lu es in t h e Va l uessection and t hen a re used to ca rry t hose va lues into equa tions in theEq uat ions sect ion or a wh en sta t ement .

Any expression of any ty pe ma y be assign ed to aval. Theextractcomma nd uses thedfilea nd t he informa tion in th e Va lues section to

a ssign va lues tovals.

Stat e decla r ati onsidentify va ria bles to be used to model discrete timesimulat ion a nd specify their units. Sta tes ca n be initia lized a nd can bea ssigned values in wh en sta t ements a nd in the va lues an d equat ionssections of the templa te.

Simu la t i on var iab le(simvar) declarationsa r e opt ion a l. You d o n ot h a v eto declare simva rs beca use their defi nition is part of the simula tor.Simva rs ar e pre-defi ned varia bles tha t pass informa tion from the

simulator to the template or from the template to the simulator. Youma y use only t he na mes pre-defi ned in the MAST lan guage a s th ena mes of simvars.

Exter nal declar ati onsident ify pa ra meters, a rguments, and pinsbrought fr om a high er level to a low er level templat e.

For eign declar ati onsident i fy foreign funct ions and foreign sta tes . Therea re tw o kinds of foreign functions: those th a t r eturn a single numbera nd t hose not restricted to return ing a single number. Foreign st a tes

a re used for mixed-simula tor a pplicat ions.

Group declar at ionsa r e a w a y t o g rou p v a r ia b les t og et h er for ext r a ct iona nd for other purposes.

Templ ate decla r ati onsdescribe a templa te. This t erm refers to th eentire templat e forma t.

I mpl ic i t declar at ionsa re those tha t occur a s a product of oth erdefi nitions an d declar a tions, a nd d o not r equire explicit declara tion.Va riables tha t a re declar ed implicit ly include th rough a nd a crossva ria bles (decla red implicitly by pin defi nit ions), simvar s, connection


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point a ss ignment s used in net l is t s t a t ement s, externa l t empla tes , node

na mes, and net na mes.

Va riable na mes fall into tw o ca tegories: units a nd pins, and a ll oth erv a ria bles. I n a t em pla t e, t h e n a mes of pin s a n d u nit s m us t a ll be d iffer en t , bu tt h ey n eed n ot be d if fer en t fr om ot h er v a r ia b le n a m es. For exa m ple, t h er e m a yexist both a unitvand a var iab lev.

The follow ing sections describe th e va ria ble types in more deta il.

Unit and Pin Definitions

Th e M AS T l a n g ua g e let s y ou d efi n e u nit s for u se in d es cr ibin g s ys t em s. U n i ts

appear in:

Defini t ions of pin-type connect ion points

D ecla ra t ions ofvar,ref,state, andvalconnection points

U nit defi nitions must precede a ny declara tions tha t use th em.

Sta nda rd unit and pin defi nit ions are in the fileunits.sin. This fi le isincluded in t he fi leheader.sin. Norma lly, th is fi le is included aut oma ticallyby use of pre-loa ded templat es, so if you w ish t o use the sta nda rd defi nitions,you do not need to a dd unit a nd pin defi nitions to your templat e.

NOTE

I f you ent er t he saber command w it h no cont r adi ctory

opti ons, it defau lt s to th e -la opti on. Thi s l oads th esaber load file analogy.sld at the top level of a system.Th is i s a pre-compi led file made f rom analogy.sin usingth e -p opti on. The stand ar d an al ogy.sl d file conta i nsheader.si n, whi ch i ncl ud es un i ts.si n. The spi ce.sl d fileal so conta i ns header.si n.

To d efi n e n ew u nit s or pin s, or t o ch a n ge d efi n i t ion s, t h er e a r e s ev er a l opt ion s.

C ha ngeunits.sinand runsaber -pt o pre-compile it for in clusionwith the-laoption.

C ha ngeunits.sina nd includeheader.sina t t he top level of th esystem h iera rchy, an d do not use th e-laoption. (The fi le ca n beincluded by writ ing


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Write new defi nit ions of units and/or pins in the template before they

a re used in declara tions. P ins a nd unit s cannot be redefi ned, so youcannot change pin a nd unit defi nitions in th is wa y.

You may place unit a nd pin defi nitions above the header, in th e headerdecla ra tions section, or in the local decla ra tions section. Rega rdless of w hereyou pla ce th em, they a re global to th e entire system description.

Unit Definitions

U n i t d efi n i t ion s ca n t a k e on e of t w o for ms a n a l og or d ig it a l . Th e a n a l og for mof aunitdefi nition is as follows:

unit { "symbol", "un i t", "definition" } identifier

where identifieris t he n a me bein g d efi n ed , a n d t he t hr ee st rin gs give t he un ita bbreviat ion, t he full unit na me, an d t he unit description, respectively.

Examples ofunitdeclar a tions are:

unit {"V","Volt","Voltage"} v

unit {"A","Ampere","Current"} i

unit {"rpm","Revolutions/minute","Angular velocity"} w

unit {"kg.m","kilogram meter","Torque"} t

Logic st a tes use th e follow ing formunitdefinition:

unit state {MASTname,"Bool ean val ue","pr in tmap","plotmap",MASTname,"Boolean val ue","pr in tmap","plotmap"}name= MASTname

There must be as ma ny lines in th e unit defi nition as th ere a re sta tes in the

unit sta te. Tw o discrete logic fa milies ar e provided, logic_4a nd logic_3. Thelogic_4 unit defi nit ion describes four-st a t e logic (0, 1, X, Z); th erefore, it ha sfour lines. The logic_3 unit defi nit ion (0, 1, Z) ha s t hr ee lines. By conven t ion,t he n am e of t he un it islogic_number, w h er e numberr efer s t o t h e n um ber oflogic st a tes.

Ea ch line ha s four entries tha t provide all th e informa tion needed for one of

the sta tes.

The fi rst entr y in the defin ition is the MASTnamea ssigned to the sta te. Thisis the na me used in the MAST lan gua ge for t he va lue of th e sta te. Forexam ple, one of t he MASTnamesfor th e logic_4 fam ily isl4_0, w hichcor res pon d s t o t h e log ic s t a t e of 0. Astate va r iab le decla red as a log ic_4 typeca n be a ssigned to bel4_0.


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Pin Definitions

P in-ty pe conn ection point s need to be defi ned in term s of th e units t hey w illuse.

NOTE

I t is gener al ly u nn ecessar y to i nser t th i s secti on in atemplat e, because stand ar d pin defini t i ons ar e specifiedin th e un i ts.si n fil e. Thi s file is aut omati cal ly i ncludedwhen you load t he Saber simul ator.

The tw o general forms of a pin d efin ition a re:

pin identifieracross un i t1through un i t2pin identifierthrough un i t1across un i t2

In th is example, identifieris t he n a me of t he pin t ype bein g d efi n ed , a n d un i t1a nd un i t2a r e t he t hr ough a n d a cr oss un it t ypes t ha t a r e t o be a ssocia t ed w it htha t pin t ype. Exa mples of pin ty pes cont a ined inunits.sinare :

pin electrical through i across v

pin rotational through w across t

Once you ha ve defi ned t hese pins (for exa mple, inunits.sin), you can usethe defi nition to declare t he types of pins in a templat e.

Across var i ablesa re those whose va lues a re equa lized w hen tw o or more pinsa re tied together a t a node (a s, for exam ple, volta ge in electr ica l syst ems).Across varia bles follow a genera lized K VL la w : the sum of across va riables

around a closed loop is zero.

Thr ough var iabl esa re th ose (like current in electrical sys tems) wh ose va luesfollow a genera lized KC L law : the sum of through var iables flowing out of anode is zero.

Connection Point Declarations

Na ming a var iable and specifying its type is ca lled a declaration. There a refour kinds of connection points t ha t you ca n decla re in a templat e:

pin-t ype

st a t e

va r

ref


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P ins a re an a log connection points t ha t use th rough an d a cross varia bles (for

elect r ica l cir cu it s, t h es e a r e u sed t o f or m K C L a n d K VL eq u a t ion s). Wh en y ouspecify them in t he template hea der an d declare th em in the hea derdecla ra tions section, pins a re ava ilable for externa l connection. When y oudeclare them in the local declarations section, pins can be internal nodes.

A pin decla ra tion identifi es the ty pe of node to w hich a pin ma y be connected.The genera l forma t of pin decla ra tions is th e follow ing:

pintypei d[, id ... ]

wh ere the pintypeis a word already specified in a pin defi nit ion, a nd th e i dsa re the na mes of th e pins being declared.

An exam ple of a pin decla ra tion is th e follow ing:

electrical c,b,e,s

This decla res th a t t he four pinsc,b,e, andsa reelectricalpin-t ypeconnection points. An automatic side effect of this declaration is that the

simulat or implicit ly ma kes ava ilablev(c),v(b),v(e), andv(s)(w ithrespect to g round) as ac ross system var iab les ; i t makesi(c),i(b),i(e), a ndi(s)as th rough system va ria bles.

Although it is recommended th a t pins be declared, t hey do not ha ve to bedeclared if you use them in a n etlist sta tement w ithin th e same templa te.

P in n a mes ca n be in teger s a s lon g a s t hey a r e used on ly in a n et list . I f y ou usenon-integer pin n a mes, you can t hen use them in other places with in th e

template. This implicit declar a tion is va lid only a fter t he netlist st a tementoccurring w ithin the t emplat e. This mea ns, for exam ple, tha t the pin na mes

could be used in a Va lues section follow ing t he netlist s ta tement , but not in aWhen statement preceding the netlist statement. The following exampleshows a va lid use of th e implicit declara tion:

template templatename a b

{

val v v

templatename2.1 a b = 1k

values

{

v = v(a)-v(b)

}

...

}

Parameter and Argument Declarations

Pa ram eters a re template va riables tha t a re used to assign va lues to otherty pes of va ria bles. They a re decla red in t he local declara tions sections. The


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st r ing

These pa ra meters use an equa ls sign (= ) to assign one a ppropria te va lue to

tha t part icular va riable.

NOTE

I f a simple par ameter is used as an ar gument, i t m ustbe in it ial ized (eit her in th e templat e or in a netl ist)otherwi se, a netl ist er r or wi l l r esul t.

I f a sim pl e par ameter i s used as a l ocal par ameter, th eSaber simu l a tor w i l l au toma t i ca l l y i n i t i al i ze i t t o undef(un less otherw ise in i ti al i zed i n t he templ ate).

Numbers

A para meter declared a s a number ty pe requires a numeric (integer or rea l)v a lu e. Th e S a ber sim ula t or u ses on ly r ea l n um ber s, s o t h er e is n o s yn t a x t h a td is t inguishes between rea l numbers and integers. The form of the decla r a t ionis :

number i d [[ =in i t i a l_value] , id [=i ni t i al_value]... ]

wh ere the i ds are the argument or para meter na mes, and t he in i t ia l_valuesa re (optiona l) num bers or expressions s pecifying init ia l va lues. Suchexpressions must consist of consta nts, pa ra meters t ha t ha ve been previouslyinitialized, or templat e argument s.

For exam ple, th e follow ing decla res severa l number declara tions on one line:

number vcc=5, dc_input, rload=10k, cload

Here,vcc,dc_input,rload, andcloadar e declared a s number typeparameter s. In addit ion ,vcc a ndrload h a v e been a s sig ned in it ia l v a lu es of 5

a nd 10k, respectively. If th ese w ere argu ment s,dc_inputa ndcloadw ouldneed to be specifi ed in a netlist entr y.

If th ese va riables were ar guments, they could be assigned values in a n etlistentry one of tw o wa ys:

1. Following th e equa ls sign, just l ist the values in the order thea rguments a re listed in the head er, separa ted by comma s

(...= 5, 2.7, 10k, 47n)


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2. List the names of the a rguments a nd assign their values in an y order

(...= cload=47n, vcc=5, dc_input=2.7, rload=10k)

For cla r it y, y ou m a y a l w a y s w i sh t o s pecif y t h e a r g um en t n a m es, r eg a r dles s oforder. Arguments w ithout initia l values assigned in t he templa te must bespecified by the netlist entry.

templatename.r efdes connecti on_poin ts= 5,2.7,10k,47n

templatename.r efdes connecti on_poin ts= dc_input=2.7, cload=47n

If th ese numbers ar e pa ra meters, you ca n a ssign them values in thePa ra meters section of th e templa te. Any simple pa ra meters ca n be used aft erthey a re declared in t he templat e by referring t o them by na me (e.g.,vcc,dc_input,rload,cload).

Enumerated Types

A para meter declared a s an enumera ted type (enum) ma y h old only one of a

r es t rict ed s et of n a m es. Th is s et of n a m es m us t be s pecifi e d w i t hin br a ces{ }

when declaring theenumpara meter.

The form of th e decla ra tion is:

enum {eval ue [, eval ue...]} i d [ [=in i t i a l_value] , id [=i ni t i al_value]... ]

wh ere the i ds ar e the arguments or pa ra meters being declared, an d theevalues, w h ich a r e n a m es, a r e t h e v a lu es t h ey m a y con t a in . Th e evaluenames,once declared, a re mean ingful in th e template, an d no other va riables orevaluesm a y h a ve t he sa m e n a me. Th e in i t ia l_valuesa re t he evaluesassignedtoi ds as initia l values.

An exa mple of a nenumdeclara tion is:

enum {_n,_p} bjt_type = _n

which declaresbjt_typeto be an a rgument or par ameter tha t can a ssumeva lues of only_nor_p. In t his example,bjt_typeha s been assigned a n

initial va lue of_n. You can use enumerat ed types in a ssignments a nd incompa risons; you ca n a lso pas s th em to foreign routines.

I f t his w er e t he d ecla r a tion of a n a r gum en t, y ou could a ssign it a va lue fr om an et lis t en t ry by a s sig nin g on e of t h e en um er a t ed va lu es t objt_type. (Again,t h e a r gu men t n a m e is n eces sa r y on ly if t h e a r gu men t s a r e t a ken ou t of or der.)

B eca use the declar a tion in the templat e specifi es an init ial va lue, it is notn ecessa r y t o specify it in t he a r gum en t list of a n et list en tr y if y ou w a n t t o usetha t va lue:

templatename.r efdes connecti on_poin ts= bjt_type=_n

If th e declara tion is for a para meter, you ca n a ssign it a va lue in the

Pa ra meters section or use th e initial va lue by not a ssigning a value. You ca n


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These parameter t ypes a l low you to group mult iple pa rameter s (either s imple

or composite) togeth er, providing convenience an d fl exibility w hen w orkingw ith la rge numbers of pa ra meters.

Structures

A structure is a pa ra meter tha t declares a n ordered list of other par a meters.The most genera l form of structu re decla ra tion is a s follow s:

struc [structurename]{declaration

declaration

...

} i d [=in i t i a l_value] [,i d [=i ni t i al_value]... ]

Note tha t t he structure i dcomes a fter t he closing bra ce.

Aside from th e keyw ordstruc, the st ructur e decla ra tion consist s of fourma jor components: t he st ructure na me (structurename), th e decla ra tions ofpara meters w ithin the structure, the i ds of the para meters being declared a s

insta nces of the st ructure, and, optionally, th eir init ial va lues.Follow ing is a n exam ple of a structure declara tion:

struc fred {

enum {_n,_p} type

number is,beta,cj

} bjt

st ruct ure I t is oft en convenient t o w ork w it h ma ny rela ted va ria bles

a s a unit . An exam ple of such a gr ouping is th e modela rgum ent of a semicondu ctor device such a s a bipolarjunct ion t r ans is tor, which is decla red as a s t ructure. Thisstructure in t urn, declares several dozen r ela ted simplepara meters tha t can a ll be ca lled by the na me of thestructure,model.

union I t ma y be necessa ry for a single a rgument or pa ra met erto hold different types of informa tion a t different t imes,on e t ype a t a t im e. An exa m ple of t his kin d of gr oupin g isthe tra nsient (tran) a rgum ent of the volta ge sourcetempla te, wh ich is decla red a s a union. This un ion, in

turn , declares both st ructures and enumera tedpara meters, only one of wh ich can be active a t a t ime.Th a t is, a s sig nin g a va lu e t o on e m em ber of t h e u nion in anetlist entry overrides a ll the oth er members of tha tunion.


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This example declares a single argument or pa ra meter na medbjt. This

va riable is a st ructure of the ty pe w hose na me isfred. It conta ins foursubordinate parameters (type,is,beta, andcj). The pa ra metertypeis anenumerat ed type, whileis,beta, andcja re numbers.

U sing th is declar a tion, it is now possible to refer directly to the st ructure

name (fred) a s a shortha nd w ay of declar ing a ddit iona l structure argumentsor parameters:

struc fred m1,m2

wherem1a ndm2ar e declared a s structures, th e same asbjt.

It is not necessary to declar e a st ructure nam e (such a sfred). The followingsingle declara tion a ccomplishes th e sa me purpose a s t he a bove tw o:

struc {

enum {_n,_p} type

number is,beta,cj

} bjt,m1,m2

On t he other ha nd, it is possible to sepa ra te completely th e declar a tion of th estructure na me from th e declara tions of the argument s or para meters tha tha ve tha t st ructure, as follow s:

struc fred {

enum {_n,_p} type

number is,beta,cj

}

struc fred bjt,m1,m2

You ca n refer to argum ent st ructures from netlist ent ries by assigning va luesto the par a meters w ithin t he structure. These are enclosed wit hinparent heses w hen a ssigned values from a netlist entry. The na mes of thepara meters wit hin t he structure need to be specifi ed only w hen th ey are notgiven in order (a lthough for ease in read ing netlist entries, you may w a nt to

specify them):

templatename.r efdes connecti on_poin ts=bjt=(type=_p,is=1a,beta=100,cj=10p)

If th e para meters of a str ucture ar e not a ssigned initia l values, but th e

structure itself is assigned a va lue of()in t he netlist entry, all of itspara meters are given the valueundefw hen simulated.

If th e structure is a para meter, the value assignment in the Pa ra meterssection is simila r.

You can a ssign initial values to th e pa ra meters with in the structure in twoplaces: wit hin a structure declara tion or follow ing th e para meter na me. The

next exa mple declar es a str ucture w ith t hree number para meters:a,b,c.


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union source {

number dc

struc {

number mag

number phase

} ac

} input1=(dc=5), input2=(ac=())

The decla ra tion decla res a sin gle union t ype, na medsource, and t w o unioni ds:input1,input2. The decla r a t ion ofsource consis t s of two opt ions :dc (anumber type para meter) a ndac(a structure type para meter w ith tw onumeric fi elds,maga ndphase). From this, you ca n see tha t t here is nestingcapa bilityone of the members of the union grouping is a str ucture (ac)w hich also consists of a grouping.

You can create the same effect with the following declarations (the names of

the unions an d th eir declar a tions ca n a lso be specifi ed as sh ow n):

union source {

number dc

struc {

number mag

number phase

} ac

}

union source input1=(dc=5), input2=(ac=())

Init ializing unions is similar to initia lizing st ructures. The difference is th a t

you must a lso specify t he na me of the choice to be in effect. In th e aboveexample,input1is init ia lized to th e choice ofdcw ith a numeric value of 5.Input2is init ia lized to the choiceac, using init ia l values defi ned within t heacst ructure. Sincemaga ndphasew ere not assigned initia l values there,input2inheritsmag=undefa ndphase=undef.

To reference a un ion a rgum ent fr om a netlist entr y, you need to include,

w ithin pa rentheses, the na me of the choice to be activat ed and its a ssignedvalues.

templatename.r efdes connecti on_poin ts=input1=(ac=(mag=1,phase=0))

To reference a un ion from inside a t emplat e, you must fi rst determin e thedecla ra tion th a t t he union activa tes. To do this, use th e int rinsic functionunion_type, w hich is described in I ntr in sic Functions and Valu es. Afterusing th is function, you can a ccess the st ructures using th e symbol->

(str ucture reference) a s follow s:

input1->dcinput2->ac->maginput2->ac->phase


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Wh en a u nion pa r a m et er is pa s sed t o a f or eig n r ou t in e, a n in d ica t i on of w h ich

choice i s a ss igned is ava i lab le to the foreign rou t ine. The det a i ls of the pass ingconvent ions a re shown in For eign Functions.

Arrays

J ust a s it is useful to creat e composite type para meters to group together

many parameter s of possibly d issimi la r t ypes , i t a l so des ir ab le to keep severa lid en t ica l t y pes t oget h er a n d t o r efer t o t h em by a sin gle n a m e. You ca n d o t h isw it h a n a r ra y. You ca n d ecla r e a n a r ra y t o be of fi x ed s ize (like a s tr uct ur e), orof unbounded size (unlike a st ructur e).

On ly a r gu men t s, pa r a m et er s, a n d s ta t es (of a fi x ed s ize) m a y be d ecla r ed t o bea rra ys. Use the follow ing synta x to declare a simple a rra y:

type i d [subscripts]

where typeis on e ofnumber,enum,string, orstate id , a n d i dis t he n am e ofthe va riable being declared a n a rra y, and t he subscriptsact as identifyingn um ber s t h a t d is tin gu is h a m on g t h e m em ber s of t h e a r ra y. Mor e t h a n on e s et

of subscripts indicat es a mu lti-dimensiona l ar ra y. The subscripts th emselvesa re a comma -separ a ted list of simple subscripts, wit h ea ch simple subscriptgiving an optiona l low er bound a nd a n upper bound:

[lower:upper, lower:upper, ...]

The low er bound on a ny of the individua l subscripts m a y be omitt ed, an d if itis, it defa ults t o 1. The synt a x would th en be:

[upper, upper,...]

In a ddition, the upper bound of the fi rst simple subscript ma y be specifi ed asan as ter isk (*), ind ica t ing a va r iab le-leng th a r r ay whose leng th is determineda t ru n-time:

[*,lower:upper,...]

It is not possible to have a rra ys in w hich t he second a nd h igher subscriptsha ve var iable lengths.

Some examples of a rra y declara tions ar e the following:

number tc[2]

number samples[*,0:1]

number x[0:50,5,-1:+1]

In the examples above,tcis a one-dimensiona l a rra y of 2 numbers;samples

is a tw o-dimensiona l ar ra y, of w hich t he fi rst dimension is not declar ed untilrun t ime, and t he second dimension sta r ts a t 0 a nd ends a t 1;xis a th ree


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dimensiona l ar ra y w hich ha s a fi rst dimension of 0 to 50, a second dimension

of 1 to 5, an d a th ird d imension of -1 to 1.

These a r r ays can be in it i a lized by including the appropr ia t e number of commasepa ra ted entries betw een squa re brackets.

number tc[2]=[0,1]number y[0:2,2,-1:1]=[1,2,3,4,5,6,7,8,9,10,11,12]

If you wa nt t o a ssign values to a rra ys, you must use squa re bra ckets.

The elements of multidimensiona l ar ra ys a re stored w ith t he last subscriptva rying fi rst (by row). This convention is th e same as t ha t in P a sca l, but t heopposite of th a t used in FORTRAN. The only t ime you need t o know th is isw hen passing t he ar ra ys to a foreign routine. The Cha pter on ForeignFunct ionsdescribes th e deta ils of passing va riable length a rra ys t o foreignroutines.

Arrays of Composite Types

Arra ys of composite or nest ed composite type par a meters ca n be decla red byputt ing the square bra ckets a f ter the i dof th e para meter. For exam ple, th efollowing d eclare a structure conta ining tw o number par a meters(breakpoint,increment) a s an element of arra yssvbea ndsvbc:

struc{

number breakpoint, increment

} svbe[*],svbc[*]

or

struc sa_points{


}

struc sa_points svbe[*],svbc[*]

In both these examples,svbea ndsvbcar e one-dimensiona l arra ys w ith th e

number of structures they conta in determined at run t ime. Ea ch member(structure) w ithin th ese a rra ys ha s tw o numbers:breakpointa ndincrement.

You ca n initia lize the a rra ys by setting ea ch st ructure equa l to pa renthesized

sets of two numbers, separa ted by comma s a nd enclosed in squa re brackets.The following example declaressvbeto be a va riable-sized a rra y of

structures.

struc{


} svbe[*]=[(-1k,10),(-10,.1),(0,.1),(10,10),(1k,0)]


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Init ially, its size is set t o five by the fi ve pairs of numbers enclosed in th e

s qu a re br a cket s. B eca u se t h e fi e ld n a m es a r e n ot n a m ed in t h e n um ber pa i rs,t h e s im ula t or con sid er s t h e n um ber s in ea ch pa ir t o be in t h e s a me or der a s inthe str ucture declar a tionbreakpointfi r st ,incrementsecond. Specifyingvalues for th ese arra ys a s a rguments or a s para meters requires the sa mesynt a x as the initializer.

Nested Composite Types

Th e m em ber s of s tr uct ur es a n d u nion s m a y be a n y of t h e pa r a m et er t y pes. I na ddition, they ma y be declared a s fi xed- or va ria ble-length a rra ys.

An exa m ple of t h is is t h e follow i ng d ecla r a t i on of a s ou rce, s im ila r t o a v olt a g es ou rce. N ot e t h a t t h e u nion a n d s t ru ct u re i ds (tran a ndsource, respectively)

come a fter t heir closing bra ces.struc {

number dc

union {

struc {number off,ampl,freq,ph;} sin

number pwl[*]

} tran

struc {number mag,phase;} ac

} \

source

This example declaressourcea s a structure with three members

(presumab ly to be used wi th three dif ferent ana lyses):dc (a number),tran (aunion, mean ing a choice of tw o va lues or w a veforms ), an dac(a st ructur e).Within thetranunion, tw o possibilities exist: th e structur esin, and theva riable-length a rra y,pwl.

I f you wa ntedsourceto be a n a rra y of length 3, you could achieve th is byreplacing th e last line of th e structure declara tion a bove bysource[3].

This example i llust ra tes tw o syntax fea t ures not yet discussedthe semicolon(;) a nd the ba ckslash (\ ). The syn ta x requirements of a structure include the

need for a n end-of-line just before th e closing bra ce. H owever, for rea da bilityyou ca n keep the bra ce on t he sa me line as t he last declara tion if you use thesemicolon, a s a bove. The ba ckslash is a cont inua tion chara cter, mea ning t ha tthe next line is to be trea ted a s a continua tion of the line with t he backsla sh.

This is simply t o enh a nce rea da bility.

The four syn ta x exa mples below a ssign va lues t osource. This synt a x willw ork when d ecla ring init ia l values for source in t he nested composite type


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where templatenameis the na me of the template from which the argum entdefi nit ion is to be borrow ed, argumentnameis the nam e of an argumentwithin templatename, and the i ds ar e the names of the argum ents orpara meters being declared t o be of the sa me type as argumentname.Assuming tha t th ere is a templat e with the na me q, and i t has a n a rgumentw it h t he n am emodel, y ou ca n d ecla r e v a r ia b les n a m edm1 a ndm2 t o b e of t hesa me type with the following d eclara tion:

q..model m1=(), m2=()

With t his declara tion, the tw o va riablesm1a ndm2can be used whenever th emodela rgument of theqtemplat e is required. In part icular, if th emodel

argument ofqis a la rge structure, thenm1a ndm2a re also large structures,with the sam e subordinate para meter na mes and an y exist ing defa ult values.

B eca use it is possible for t emplat e defi nit ions t o be nested, it is a lso possiblef or a r g def s t o r ef er t o a r g um en t s in t h e n es t ed t em pla t es. Th e g en er a l for m isas follows:

template1..template2..template3..argumentname

with as m an y templat e names as a re needed to rea ch th e required a rgument .For exa m ple, t h er e m a y be a t em pla t enand, t h a t u ses it s pr iva t e d efi n it ion ofa M OS t r a n sis t or ca l ledmos. You cou ld d ecla r e a n a r gu men t t o be of t h e s a metype as t hemodelargument withinmos, as follow s:

nand..mos..model m1

Argdefs are initialized to the same para meter na mes and initia l values a s inthe defi ning argument . I t is as i f the i dwere listed aft er the structure a sfollows:

data_structure {

declarations

} id=()

You can supply a dditional initializa tion informat ion w ith th e same synta xused to initialize other i ds of the da ta structure. In th e example usingq..model, assume th a t one of the member para meters isbf. The following

statement initializesbfto a value different from the default :

q..model m1=(bf=80)

Arrays of argdefs

If an a rgument or para meter is defi ned as an a rray of argdefs, and thea r gu men t u sed in t h e d ecla r a t ion is it self a n a r ra y, t h e r es ult in g v a ria b le w illbe a n a rra y w ith th e subscripts in the argument s appended to the subscripts

used on the a rgdef decla r a t ion . This i s bes t expla ined by an example. C ons idera templat elowlevel, wit h t he follow ing declar a tion for one of its a rguments:

number lowarg[5]


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struc {number vo,va,f,td,phase;}sin

} tran

tran->sin->phase

Similar ly, you ca n use the sa me opera tor w ith a n a rra y. An a rra y reference

ha s t he following genera l form:

var iab le[expression,expression,...]

w here ea ch expressionmust, w hen evalua ted, be a n umber (real numbers a reconverted to integers by truncation).

An exam ple of a n a rra y reference is shown below :

struc {

number work[32]

} m1[*]

m1[i]->work[32]

where arra yworkis a member of ar ra ym1[i](a n a rray of arra ys), andm1[i]->work[32]represents one of its element s.

Structure Overlay

St ructure overlay decla ra tions let you assign th e values of a compositepa rameter to another compos it e pa rameter, and then change va lues of specific

members. The general syn ta x for t his a ssignment is:

left_hand_value=structurename


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Declar ati on Oper ators



You could then cha nge t heisa ndrbva lues formodel2by using thestructure_overlaywi thmodel1:

#in parameters section

model1=(is=1e-14,bf=100)

model2=model1is=1e-15

model1->rb=10with:

model1=model2


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Declar ati on Oper ators



freq_phaseis set t o 1 during frequency domain a na lyses tha t

comput e the pha se of complex numbers. It is set t o 0 otherw ise.

statisticalis set t o 1 when Mont e Ca rlo a nd other sta tisticala na lyses are being performed. It is set to 0 otherw ise. It ca n be usedonly in the Pa ra meters section and in t he netlist .

timeis set (continua lly updated) to the simulat ion t ime at w hich t hetempla te is being eva lua ted. Time progresses only du ring t ime domaina na lyses. Time is set to 0 in frequency a nd D C d oma in a na lyses in t heValues and Equations sections for analog-only simulation.For

templa tes providing mixed-mode simula tion (i.e., cont a ining Whensta tements), th e value of t ime is dependent on th e DC Algorithmoutlined in The DC Algorithm on page 9-11.

time_domainis set t o 1 during a ny t ra nsient a na lysis. It is set to 0otherwise.

time_initis set t o 1 a t the sta r t of t ransient a na lysis . I t is set t o 0otherwise. I t is not r eset wh en resta r t ing a t ra nsient an alysis from aprevious one. It is used primarily in When statements.

tr_startis set to 1 a t t he sta r t of any tra nsient a na lysis , includingone resta rted from a previous tra nsient a na lysis. It is set t o 0

otherwise. It is used prima rily in when sta tements.

tr_doneis set to 1 a t th e end of a ny t ra nsient a na lysis. It is usedprimarily in When sta tements.

time_step_doneis set to 1 a t t he end of each time step in t ra nsienta na lysis. It is used primar ily in When sta tements.

Category 2

next_timecan be set by th e template to a future t ime tha t t hesimulat or must reach exa ctly. If th e templa te ha s no scheduling

requirement s, it should leavenext_timeundefi ned. A ty pica l use ofth is simvar is in piecewise linear sources, where it t ells th e simulatorw hen t he next t urning point occurs in the defi nition of source, or an y

other t ime-dependent t empla te w here an abrupt cha nge occurs.Another use is to ensure tha t t he simulator uses a pa rticula r t ime.More informa t ion abou t usingnext_time i s prov ided in the subsect ion

tit led Scheduling Ana log Wa veform Sa mpling Times.

step_sizecan be s

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