Scicos Block
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Left shift circulate integer modulo function block

Contents

• Left shift circulate integer modulo function block
  • Palette
  • Description
  • Dialog box
  • Default properties
  • Interfacing function
  • Computational function (type 2)
  • See also
  • Authors

Palette

• NonLinear.cosf - NonLinear palette

Description

This block realizes a left shift circulate integer modulo. The output is the left shift circulate N bit of the input word, define by a word of Nbit nbit using the 2 complement arithmetic notation. The values of the output are comprise between $\left[-2^{Nbit-1};2^{Nbit-1}-1\right]$. This function is caracterized by a non-constant amplitude. Following the number of shift, this non-linearity takes different slope. Fig. shows example for a given parameter Nbit=5, for one shift and two shift.

Figure : Plot of nonlinear function lcmodulo for Nbit=5. (a) One shift; (b) Two shifts

This function is modelled with binary operators of C language. First block begins to convert input value, defined in 2 complement arithmetic notation, in an unsigned integer value. After he realizes N times the left shift. Table. shows necessary stages to realize a left shift circulate operation for an integer value defined with 8 bits.

Table: Stages of a left binary shift circulate operation

Stages	Operations	Decimal	Binary
1	Read unisigned integer value	150	1001 0110
2	Left shift binary	300	1 0010 1100
3	Tronquate to 8 bits	44	0010 1100
4	Addition of the tronquate bit	45	0010 1101

Computational function finally converts unsigned integer value in signed integer value and puts results in output register y.

Dialog box

• Number of bit :
  Type 'vec' of size -1. The number of bit per integer.
• Number of shift :
  Type 'vec' of size -1. The number of binary left shift applied on input at each event.

Default properties

• always active: no
• direct-feedthrough: yes
• zero-crossing: no
• mode: no
• number/sizes of inputs: 1 / 1
• number/sizes of outputs: 1 / 1
• number/sizes of activation inputs: 0 /
• number/sizes of activation outputs: 0 /
• continuous-time state: no
• discrete-time state: no
• name of computational function: lcmodulo

Interfacing function

LCMODULO_f.sci

Computational function (type 2)

/* lcmodulo Scicos left shift circulate integer modulo function block
 * Type 2 simulation function - scilab-2.6&2.7&3.0
 * IRCOM GROUP - Author : A.Layec
 */

/* REVISION HISTORY :
 * $Log$
 */

#include "machine.h"
#include <stdio.h>

/* Cette fonction de simulation propose de réaliser la fonction
 * décalage circulaire à gauche modulo rencontrée dans
 * les systèmes numériques traitant les opérations sur entier en code complément à 2.
 * entrées régulières : u[0..nu-1]
 * sorties régulières : y[0..nu-1] = lcmod[u[0..nu-1]]
 * paramètres entiers : ipar[0..nu-1] : nombre de bits des mots entiers.
 *                                 ipar[nu..2*nu-1] : nombre décalage
 *
 * Rmq : l'entrée de type double est tronquée à sa valeur entière.
 *           la sortie est soit négative soit positive
 */

/*Prototype*/
void lcmodulo(flag,nevprt,t,xd,x,nx,z,nz,tvec,ntvec,rpar,nrpar,
              ipar,nipar,inptr,insz,nin,outptr,outsz,nout)
integer *flag,*nevprt,*nx,*nz,*ntvec,*nrpar,ipar[],*nipar,insz[],*nin,outsz[],*nout;
double x[],xd[],z[],tvec[],rpar[];
double *inptr[],*outptr[],*t;
{
    /*Déclaration des variables*/
    int i,j,nu;
    double *y;
    double *u;
    long ent; /*Déclaration d'un entier de type long long int*/

    /*Récupération des adresses des ports réguliers*/
    y=(double *)outptr[0];
    u=(double *)inptr[0];

    /*Récupération de la taille du port d'entrée*/
    nu=insz[0];

    for (i=0;i<nu;i++)
    {
     /*Récupération de la valeur d'entrée*/
     ent = (long) u[i];

     /*Conversion en nombre non signé*/
     ent &= (2<<(ipar[i]-1)) - 1;
     /*fprintf(stderr,"lcmodulo u=%f, ent=%d\n", u[i],ent);*/

     /*Réalisation de l'opération décalage circulaire à gauche*/
     for(j=0;j<ipar[nu+i];j++)
     {
      if((((1<<(ipar[i]-1))&ent)>>(ipar[i]-1))==1)
         {
          ent <<= 1;
          ent += 1;
         }
      else ent <<=1;
      ent &= (2<<(ipar[i]-1)) - 1;
      /*fprintf(stderr,"lcmodulo j=%d, ent_decal=%d\n",j,ent);*/
     }

     /*Conversion en nombre signé (cc2)*/
     ent -= 2<<(ipar[i]-2);
     ent &= (2<<(ipar[i]-1)) - 1;
     ent -= 2<<(ipar[i]-2);

     /*Place valeur de ent dans le registre de sortie*/
     y[i] = ent;
    }
}

See also

• IMODULO_f - Integer modulo function block (Scicos Block)
• IMODULOB_f - Integer modulob function block (Scicos Block)
• FMODULO_f - Float modulo function block (Scicos Block)
• FMODULOB_f - Float modulob function block (Scicos Block)
• FMODULOC_f - Float moduloc function block (Scicos Block)

Authors

IRCOM Group Alan Layec