The local high speed bus standard SPI-4.2 has already been the universal interface standard for signal transimission between the PHY device and the LINK device.The paper describes the working principium
designing idea and circuit structure of the diagonal interleaved parity code in the SPI-4.2.And it presents a algorithm of DIP-4 which can be configured to be 16X bit width.The algorithm has been proved to be right in practice and implemented easily.