Specifications

4-11
PA-T3+ Serial Port Adapter Installation and Configuration
OL-3505-03
Chapter 4 Configuring the PA-T3+
Configuring the Interfaces
Note Invert data only on the PA-T3+ interface or on the CSU/DSU; inverting both cancels out both data
inversions.
Configuring NRZI Format
Table 4-5 summarizes NRZI format commands. For more information, see the remainder of this section.
All EIA/TIA-232 interfaces on the PA-T3+ support 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 absence of data—a space—at the beginning of a bit interval as a signal transition and
the presence of data—a mark—as no signal transition. NRZI uses relational encoding to interpret signals
rather than determining absolute values.
NRZ format—the factory default on all interfaces—is more common. NRZI format is commonly used
with EIA/TIA-232 connections in IBM environments.
Enable NRZI encoding on any interface using the nrzi-encoding [mark] command, where no argument
after the command is interpreted as a signal transition, and mark is interpreted as no signal transition.
This command functions in the same way on all supported platforms. Before you can enable NRZI
encoding, you must use the interface serial command (followed by the interface address of the interface)
to select the interface on which you want to enable NRZI encoding.
In the example that follows, NRZI encoding with a signal transition—no argument—is specified:
Router(config-if)# nrzi-encoding
In the example that follows, NRZI encoding with no signal transition—with argument—is specified:
Router(config-if)# nrzi-encoding mark
Table 4-5 NRZI Format Commands
Purpose Command Example Further Information
Enable NRZI
encoding.
nrzi-encoding
[mark]
1
1. Mark is an optional argument. When mark is used, it means there is no signal transition; there is data (a mark) at the beginning of a bit interval. When
mark is not used, it means there is a signal transition; there is no data (a space) at the beginning of a bit interval.
The example is for a serial interface with NRZI
mark encoding specified:
Router(config)# interface serial 3/0
Router(config-if)# nrzi-encoding mark
The example is for a serial interface with NRZI
space encoding specified:
Router(config)# interface serial 3/0
Router(config-if)# nrzi-encoding
“Configuring Cyclic
Redundancy Checks”
Disable NRZI
encoding.
no nrzi-encoding The example disables NRZI encoding on a serial
interface:
Router(config)# interface serial 3/0
Router(config-if)# no nrzi-encoding
“Configuring Cyclic
Redundancy Checks”