Nrz And Nrzi Formats; Cyclic Redundancy Checks (Crcs) - Cisco 7000 Hardware Installation And Maintenance

Figure 2-33
Figure 2-34
Caution
jackscrews on the DB-15 connector backshell are securely screwed down while the FSIP is
operating.

NRZ and NRZI Formats

All interfaces support both nonreturn to zero (NRZ) and nonreturn to zero inverted (NRZI) formats.
Both formats use two different voltage levels for transmission. NRZ signals maintain constant
voltage levels with no signal transitions (no return to a zero voltage level) during a bit interval and
are decoded using absolute values (0 and 1). NRZI uses the same constant signal levels but interprets
the presence of data at the beginning of a bit interval as a signal transition and the absence of data as
no transition. NRZI uses differential encoding to decode signals, rather than determining absolute
values. NRZ, the factory default on all interface types, is most common. All interface types also
support NRZI format, which is commonly used with EIA/TIA-232 connections in IBM
environments. (See the section "Configuring NRZI Format" in the chapter "Maintenance" for
configuration instructions.)

Cyclic Redundancy Checks (CRCs)

All interfaces (except the E1-G.703/G.704) use a 16-bit cyclic redundancy check (CRC) by default
but also support a 32-bit CRC. (The E1-G.703/G.704 interface uses a 4-bit CRC).
Note
resulting display indicates Part Number 81-0050-01, Hardware Version 1.0, you cannot use the
CRC-32 feature. If the display indicates Part Number 81-0050-02, Hardware Version 1.1, you can
use the CRC-32 feature. If you are using HIP Microcode Version 1.2 and Maintenance
Release 9.17(7) or earlier, the system will default to a 32-bit CRC. If you are using HIP Microcode
Version 1.2 and Maintenance Release 9.17(8) or later, the system will default to a 16-bit CRC. If you
are using HIP Microcode Version 1.3, any software release will cause the system to default to a
16-bit CRC.
E1-G.703/G.704 Interface Cable for 120-Ohm, Balanced Connections
(with DB-15 Connectors on Both Ends)
E1-G.703/G.704 Interface Cable for 120-Ohm, Balanced Connections
(with Twinax Connectors and Cables)
It is a requirement of the statutory approval of the E1-G.703/G.704 interface that the
To determine if your HIP will support a 32-bit CRC, use the show diag command. If the
Preparing Network Connections
Preparing for Installation 2-105