The PD98402A is one of the ATM-LAN LSIs and incorporates the TC sublayer function in the SONET/SDHbased physical layer of the ATM protocol. The main functions of the PD98402A include a transmit function for mapping ATM cells received from the ATM layer onto the payload block of the SONET STS-3c/SDH STM-1 frame and sending them to PMD (Physical Media Dependent) in the physical layer, and a receive function for separating the overhead block and ATM cells from the data string received from the PMD sublayer and sending the ATM cells to the ATM layer.