Cisco PA-8T-232, Руководство по установке и настройке

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PA-8T-232 Synchronous Serial Port Adapter Installation and Configuration
OL-3562-03
Chapter 5 Configuring the PA-8T-232 Interfaces
Configuring the EIA/TIA-232 Interfaces
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.
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
The preceding command examples apply to all systems in which the PA-8T-232 is supported.
Use the no nrzi-encoding command to disable NRZI encoding.
When you are done, press Ctrl-Z—hold down the Control key while you press Z—or enter end or exit
to exit configuration mode and return to the EXEC command interpreter prompt. Then write the new
configuration to NVRAM using the copy running-config startup-config command.
For complete command descriptions and instructions, refer to the Configuration Fundamentals
Configuration Guide publication. For more information, see the
“Obtaining Documentation” section on
page x and the “Obtaining Technical Assistance” section on page xi .
Configuring Cyclic Redundancy Checks
Table 5-6 summarizes cyclic redundancy check (CRC) commands. For more information, see the
remainder of this section.
CRC is an error-checking technique that uses a calculated numeric value to detect errors in transmitted
data. All interfaces use a 16-bit CRC (CRC-CITT) by default but also support a 32-bit CRC. The sender
of a data frame calculates the frame check sequence (FCS). Before it sends a frame, the sender appends
Table 5-6 CRC Commands
Purpose Command Example Further Information
Enable 32-bit CRC. crc size The example enables 32-bit CRC on a serial
interface:
Router(config)# interface serial 3/0
Router(config-if)# crc 32
“Configuring Cyclic Redundancy
Checks”
Return to default
16-bit CRC. no crc size The example disables 32-bit CRC on a serial
interface and returns to the default 16-bit
CRC:
Router(config)# interface serial 3/0
Router(config-if)# no crc 32
“Configuring Cyclic Redundancy
Checks”