Encoder within a communication system that avoids encoded dc accumulation and can use coding violations to synchronize a decoder and detect transmission errors

Abstract

A communication system is provided for interconnecting a network of digital systems. Each node of the communication system may include a transceiver and an encoder/decoder. The encoder codes an incoming data stream and forwards the encoded data stream across a communication link based on a DC-adaptive encoding mechanism. The encoded data stream is substantially free of a DC value that would skew the detector components at the receiver end of the communication link. Moreover, the encoded signal is forwarded at no greater than the incoming bitstream. Encoding occurs dependent on a digital sum value of the preceding clock cycle (DSV ) for the encoded bitstream and the logic values for the incoming bitstream during the current clock cycle n as well as the subsequent clock cycle n+1. Encoding according to normal encoding or multiple-ones encoding is dependent on those values. A coding violation can be used within a preamble to synchronize a decoder, detect transmission errors, and to quickly lock the phase-locked loop within the receiver.