Replacing Serial Port Adapter Cables - Cisco 7000 Series Hardware Installation And Maintenance Manual

Installing and Configuring Processor Modules
To disable CRC-4 and return to the default of no CRC error checking, specify the slot and port
address and use the no crc4 command. For complete command descriptions and instructions, refer
to the related software documentation.

Replacing Serial Port Adapter Cables

The port adapter cable connected to each FSIP port determines the electrical interface type and mode
of the port. The FSIP ports are not configured for either DTE or DCE mode by default. When there
is no cable attached to a port, the software identifies the port as Universal, Cable Unattached rather
than either a DTE or DCE interface. When a cable is attached, the port recognizes the mode and
automatically uses the clock signal from the appropriate source (external for DTE or internal for
DCE).
Although you do not have to configure a clock source for the ports, you do have to define the clock
speed the first time you configure a port as a DCE interface. Because the ports automatically use the
appropriate clock source for the type (mode) of cable it detects, you can configure a clock rate for a
DCE interface and later replace the DCE cable with a DTE cable; the FSIP will ignore the internal
clockrate unless it detects that a DCE cable is attached. This configuration allows you to perform a
loopback test on a serial port without a port adapter cable attached.
Following is an example of the show controller cxbus command that shows an interface port (2/0)
that has an EIA/TIA232 DTE cable attached, and a second port (2/1) that does not have a cable
attached:
To change the electrical interface type or mode of a port on line, replace the serial adapter cable and
use software commands to restart the interface and, if necessary, reconfigure the port for the new
interface. At system startup or restart, the FSIP polls the interfaces and determines the electrical
interface type of each port (according to the type of port adapter cable attached). However, it does
not necessarily repoll an interface when you change the adapter cable on line. To ensure that the
system recognizes the new interface type, shutdown and reenable the interface after changing the
cable.
Perform the following steps to change the mode or interface type of a port by replacing the adapter
cable. If you are replacing a cable with one of the same interface type and mode, these steps are not
necessary. (Simply replace the cable without interrupting operation.)
Step 1
Step 2
5-50 Cisco 7010 Hardware Installation and Maintenance
Router# configure terminal
interface serial 3/0
crc4
^z
7010# show controller cxbus
Switch Processor 7, hardware version 11.1, microcode version 1.4
512 Kbytes of main memory, 128 Kbytes cache memory, 299 1520 byte buffers
Restarts: 0 line down, 0 hung output, 0 controller error
FSIP 2, hardware version 3, microcode version 1.0
Interface 16 - Serial2/0, electrical interface is RS-232 DTE
31 buffer RX queue threshold, 101 buffer TX queue limit, buffer size 1520
Transmitter delay is 0 microseconds
Interface 17 - Serial2/1, electrical interface is Universal (cable unattached)
31 buffer RX queue threshold, 101 buffer TX queue limit, buffer size 1520
Locate and remove the adapter cable to be replaced.
Connect the new cable between the FSIP port and the network connection. Tighten the
thumbscrews at both ends of the cable to secure it in the ports.