Control unit for the common memory of an atm node

Abstract

An apparatus and method for controlling the common memory of an ATM-node. The nodes serve for the continuous reception and onward routing of address-labelled cells with uniform length and uniform construction. The apparatus includes means for management and control and a sequencer for managing the storage blocks of the common memory and for controlling the sequential reading in and reading out of cells, respectively, into or out of said storage blocks. The circuits for management and control include at least one addressable read/write store, a monitor logic, an input logic, a bus- and control-logic, and a comparator, the read/write store includes a number of storage locations equal to the third plurality plus two times the second plurality multiplied by the quantity, plus 2. Every storage location of the read/write store is constructed for storing an address. Two times the second plurality of the storage locations multiplied by the quantity is associated in pairs with the outgoing lines, and the third plurality of storage locations is associated with the storage blocks of the common memory. Two of the storage locations are associated with the empty storage blocks of the common memory. The method includes providing lists for each queue and empty storage blocks the common memory. Each list has a head element and a tail element. The elements of the lists are addresses and the total of all the elements of all of the lists is constant and is equal to the number of the storage blocks of the common memory. The method also includes appending a current head element of the list of the empty storage blocks as a new tail element of the list of empty storage blocks when storing a cell to the common memory, and appending a current head element of a list associated with a queue in the common memory as a new tail element of the list of the empty storage blocks.