Bi-directional 3-port ATM CAM supporting fast look-up and reduced cycle time

This paper presents an architecture of a bi-directional 3-port ATM CAM. It satisfies one of the fundamental requirements that ATM cell header translation has to be performed in real time. It also reduces the access cycle time to get a retrieval header and reduces the header converted as a result of the match processing. The proposed architecture is composed of three access ports. Each port operates independently of each other. To realize this 3-port function, a bit architecture based on the presented requirements of the functional ATM CAM is proposed. Using such a bit architecture, an architecture of CAM part which includes each module for GFC, VPI, VCI, and PTI field, is also proposed. To provide bi-directional translation of VPI/VCI, two CAM architectures for receiving and transmitting directions are used in each block respectively. The two CAMs reciprocate their matching addresses and the data corresponding to the addresses. It provides control cell extraction such as OAM, unassigned, and physical layer cells. It optionally provides 3-byte tagging for cell switching function for both UNI and NNI modes.