Signal sending-and-receiving circuit and self id process for node-to-node communications in serial-bus network

Abstract

A signal sending-and-receiving circuit is used for a long-distance port in a node having a state machine within a serial-bus network, wherein a sending section performs scrambling, coding and conversion on signals given from the state machine to produce serial signals which are sent onto a transmission path, while a receiving section performs conversion, de-scrambling and decoding on signals given from the transmission path to produce decoded signals. A control signal is created based on a Data_prefix signal detected from the signals of the state machine, and an Idle signal or a Grant signal detected from the decoded signals. The control signal controls a selector to selectively output either the decoded signals or a pseudo Idle signal which is newly created. Then, a collision signal is created in response to an output of the selector. Thus, it is possible to avoid collision between a grant signal and a Self ID packet, so it is possible to prevent the Self ID packet from being damaged. In addition, the state machine is designed to have six states, namely, S (Self ID Start), S (Self ID Grant), S (Self ID Receive), S (Send Speed Capabilities), S (Self ID Transmit) and S (Self ID Suspend). Herein, the state machine is placed in the state S to suspend the Self ID process until the node detects Idle at a parent port connected to a parent node after detecting Idle at a receive port receiving the Self ID packet from another node.