Nortel Circuit Card Installation Manual page 857

Fault detection
Firmware on the ESDI card detects hardware faults on the card and link level
LAPB protocol faults. It reports the faults to the CPU when predetermined
thresholds (downloaded at initialization) have been exceeded.
Fault isolation
The ESDI/Command and Status Link (CSL) maintenance software takes the
ESDI card out of service when the out-of-service thresholds are exceeded for
the following:
• LAPB error conditions (for example, retransmission, Cyclic Redundancy
Check (CRC) errors, overrun/underrun errors)
• Physical or link errors
• Detected hardware errors
Connection characteristics
The two DB-25 connectors on the front panel of the ESDI card provide
connections to each of the two I/O ports. The electrical interface of these
connectors is a modified version of the RS-422-A standard designed to drive
high-speed data over long cable lengths (up to 100 ft). Table 267 shows the
interconnection specifications for these ports.
Table 267
QPC513 interconnection specifications
Distance
<15.24 m (<50 ft)
>15.24 m and <30.48 m
(>50 ft and <100 ft)
>30.48 m (>100 ft)
QPC513 Enhanced Serial Data Interface card
Interconnection
Regular 25-conductor cable
Twisted pair for balanced circuits
Network interface devices such as stand-alone
modems or DS-1 facilities using
Asynchronous/Synchronous Interface Module
(ASIM) and Data Line card (DLC)
Circuit Card Description and Installation
Page 857 of 906