1092 QPC513 Enhanced Serial Data Interface cardEach port operates independently in synchronous mode, in half or fullduplex, at speeds of up to 64 kbps. Each port can be connected to eitherData Terminal Equipment (DTE) or Data Communications Equipment (DCE).The electrical interface for the ESDI card may be either EIA RS-232-C ora proprietary high-speed interface. The high-speed interface combinesfeatures of RS-422-A for data and timing signals with features of RS-232-Cfor control signals.Figure 310ESDI card block diagramThe QPC513 ESDI card is an intelligent controller. The local micro-processorperforms all of the overhead associated with synchronous data transfer.The system processor passes data to the ESDI card processor a byteat a time using conventional memory reads and writes. The ESDI cardprocessor stores the data in a RAM cache on the ESDI card, and passesit to the synchronous communication chip in blocks using Direct MemoryAccess (DMA) techniques.Synchronous communicationThe ESDI cards supports LAPB, a subset of the HDLC synchronousprotocol. A description of the LAPB protocol is shown in Appendix A, LAPBdata link protocol.The HDLC data link is a bit-oriented protocol. The information data bitsare transmitted transparently across the link in packets. The maximumlength of the information field for these packets is 128 octets, where anoctet consists of 8 bits.Nortel Communication Server 1000Circuit Card ReferenceNN43001-311 01.04 StandardRelease 5.0 23 May 2008Copyright © 2003-2008, Nortel Networks.
