Specifications

4-12
PA-T3+ Serial Port Adapter Installation and Configuration
OL-3505-03
Chapter 4 Configuring the PA-T3+
Configuring the Interfaces
The preceding command examples apply to all systems in which the PA-T3+ is supported.
Use the no nrzi-encoding command to disable NRZI encoding.
When you have finished, 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 4-6 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
the FCS value to the message. The receiver recalculates the FCS and compares its calculation to the FCS
from the sender. If there is a difference between the two calculations, the receiver assumes that a
transmission error occurred and sends a request to the sender to resend the frame.
Enable 32-bit CRC using the crc 32 command. Before you can enable 32-bit CRC, 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 32-bit CRC. This command functions in the same way on all supported
platforms.
In the example that follows, 32-bit CRC is specified:
Router(config-if)# crc 32
The preceding command example applies to all systems in which the PA-T3+ is supported.
Use the no crc 32 command to disable CRC-32 and return the interface to the default CRC-16
(CRC-CITT) setting.
When you have finished, 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.
Table 4-6 CRC Commands
Purpose Command Example Further Information
Enable 32-bit CRC. crc size The example enables 32-bit CRD 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 CRD 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”