3Com 3C63311 Reference Guide - Page 226

214 APPENDIX B: PATHBUILDER S330/S310 MODULE AND APPLICATION OVERVIEW Serial Interface The serial interface is designed to interconnect frame-based devices/networks and cell-based ATM devices/networks. The PathBuilder S330/S310 provides a single serial interface that can be configured as DTE or DCE and, with different cable adapters, can support V.35/RS-449/RS-530/X.21 interface to routers. The PathBuilder S330/S310 can perform cell-to-frame as well as frame-to-cell conversion. On the serial interface receive side, frames received from the HDLC serial interfaces are segmented to cells by the SAR and passed to the CTX chip where they can be switched. On the serial interface transmit side, cells received from the ATM interfaces are reassembled into frames and passed to the HDLC serial interfaces. The PathBuilder S330/S310 uses a RISC processor to perform the lookup and interworking functions between frame and ATM services. It also performs the LMI functions and collects alarms and statistics. The PathBuilder S330/S310 provides for frame relay service and network interworking (FRF 5 and 8), as well as ATM DXI and transparent HDLC operation. You can use it for interworking between the ATM network and a variety of different frame-based networks or devices such as Frame Relay and ATM DXI. The interface can be clocked up to 6.2Mbps, and it supports the following modes of operation: Internal timing-DCE provides the clock for a router. External timing-DTE receives a clock from a DCE device such as a DSU (digital service unit). The mode of operation is selected automatically (by autosensing), based on the type of cable connected to the unit-DCE or DTE. Serial Interface Frame The PathBuilder S330/S310 supports three modes of Frame-to-Cell transit services: Protocol Modes ATM DXI Mode 1A-Supported by certain routers. HDLC/SDLC-Used mainly for transparent point-to-point operation. Frame Relay Forum Specification 5 and 8; modes 1 and 2-Used to terminate a frame relay router. Each service is designed to support a different type of user application; however, all the services share the same ATM backbone characteristics. The serial port modules are mapped over ATM Permanent Virtual Circuits (PVCs).