PROCEDE ET DISPOSITIF D'ATTRIBUTION DE L'ACCES A UN BUS UTILISE EN MODE PARTAGE

L'INVENTION CONCERNE LA GESTION DE RESSOURCES PARTAGEES DANS UN SYSTEME INFORMATIQUE.DANS UN SYSTEME DANS LEQUEL PLUSIEURS DISPOSITIFS D'ENTREESORTIE 110-1, ... 110-N PEUVENT ACCEDER A LA DEMANDE A UN BUS COMMUN 105, CHAQUE DISPOSITIF DESIRANT ACCEDER AU BUS APPLIQUE SEQUENTIELLEMENT LES CHIFFRES DU CODE DE PRIORITE QUI LUI EST AFFECTE A UN BUS D'ARBITRAGE 102, POUR RESOUDRE LE CONFLIT D'UTILISATION. ON DISPOSE D'UNE PLUS GRANDE SOUPLESSE DANS L'ATTRIBUTION DE L'ACCES PAR L'UTILISATION DANS CHAQUE DISPOSITIF D'ENTREESORTIE DE BASCULES D'ETAT QUI GENERENT DES BITS DE PARAMETRES QUI CONSTITUENT LES BITS DE PLUS FORT POIDS D'UN CODE DE PRIORITE DYNAMIQUE.APPLICATION AUX SYSTEMES DE COMMUTATION PAR PAQUETS. Circuitry is disclosed for allocating requests for demand-shared bus access among a plurality of service requesting ports. During bus contention time, each requesting port synchronously and sequentially applies the digits of its assigned unique priority code to the bus beginning with the most significant digit. After the application of all digits, only the requesting port having the highest code remains in contention and it seizes the bus. A plurality of status flip-flops is provided in each port for generating port parameter bits. The generated parameter bits are applied to the bus as the most significant bits of a dynamic port priority code during contention time. However, the selective application of a mask signal to a mask conductor during contention time causes each requesting port to ignore any parameter bits on the bus as long as the mask signal remains. This returns control of the port preference to any unmasked parameter bits and to the assigned port priority codes.