Nortel Networks Circuit Card 311 - Manual (Page 1092)

1092 QPC513 Enhanced Serial Data Interface card
Each port operates independently in synchronous mode, in half or full
duplex, at speeds of up to 64 kbps. Each port can be connected to either
Data Terminal Equipment (DTE) or Data Communications Equipment (DCE).
The electrical interface for the ESDI card may be either EIA RS-232-C or
a proprietary high-speed interface. The high-speed interface combines
features of RS-422-A for data and timing signals with features of RS-232-C
for control signals.
Figure 310
ESDI card block diagram
The QPC513 ESDI card is an intelligent controller. The local micro-processor
performs all of the overhead associated with synchronous data transfer.
The system processor passes data to the ESDI card processor a byte
at a time using conventional memory reads and writes. The ESDI card
processor stores the data in a RAM cache on the ESDI card, and passes
it to the synchronous communication chip in blocks using Direct Memory
Access (DMA) techniques.
Synchronous communication
The ESDI cards supports LAPB, a subset of the HDLC synchronous
protocol. A description of the LAPB protocol is shown in Appendix A, LAPB
data link protocol.
The HDLC data link is a bit-oriented protocol. The information data bits
are transmitted transparently across the link in packets. The maximum
length of the information field for these packets is 128 octets, where an
octet consists of 8 bits.
Nortel Communication Server 1000
Circuit Card Reference
NN43001-311 01.04 Standard
Release 5.0 23 May 2008
Copyright © 2003-2008, Nortel Networks
.