Method and apparatus for providing eof for frame modification

Abstract

A multiport data communication system for switching data packets between ports comprising a plurality of receive ports for receiving data packets, a memory storing the received data packets, and a plurality of transmit ports each having a transmit queue. Logic circuitry for each transmit port controls reading of a data packet from memory, provides a control signal indicating an end of reading the data packet from the memory, decides whether a length of the read data packet is to increase, decrease, or remain the same, controls writing the read data packet to a corresponding transmit queue in accordance with the decision, and provides a signal indicating an end of writing the data packet to the transmit queue. To generate the end of reading of the data packet from memory, the logic circuitry determines a number of read operations necessary to read the data packet, corresponding to read address data from the memory, counts each read operation, and provides the signal indicating an end of reading the data packet from the memory when the counted read operations are equal to the number of determined read operations. To generate the end of writing the data packet to the transmit queue, the logic circuitry determines a number of write operations necessary to write the data packet which is modified/unmodified in accordance with decision as to whether a length of the read data packet is to increase, decrease, or remain the same, counts each write operation, and provides the signal indicating an end of writing the data packet to the transmit queue when the counted write operations are equal to the number of determined write operations.