4-3
PA-8T-232 Synchronous Serial Port Adapter Installation and Configuration
OL-3562-03
Chapter 4 Attaching a Compact Serial Cable
Determining the Port Mode
Determining the Port Mode
The compact serial cable connected to each port determines the mode of the ports (the electrical interface
type is always EIA/TIA-232). The default mode of the ports is DCE, which allows you to perform a
loopback test on any port without having to attach a port adapter cable. For information related to the
loopback command, see the
“Using loopback Commands” section on page 5-32
. Although DCE is the
default, there is no default clock rate set on the interfaces. On a Cisco 7100 series, Cisco 7200 series,
Cisco uBR7200 series router, Cisco 7301 routers, or Cisco 7401ASR router, when there is no cable
attached to a port, the software actually identifies the port as cable type: None present rather than either
a DTE or a DCE interface. On a Cisco 7304 PCI Port Adapter Carrier Card, VIP, Catalyst RSM/VIP2,
or Catalyst 6000 family FlexWAN module, when there is no cable attached to a port, the software
actually identifies the port as Universal (cable unattached) rather than either a DTE or a DCE interface.
Caution
Attach only an EIA/TIA-232 compact serial cable to the PA-8T-232 installed in your router. Attaching
a compact serial cable of another interface type to the port adapter could damage your router or the
hardware at the network end of the cable.
Following is an example of the show controllers serial command that shows a Cisco 7100 series router,
a Cisco 7200 series router, a Cisco uBR7200 series router, Cisco 7301 router, or a Cisco 7401ASR
router interface port (1/0) that has a DCE cable attached:
Router# show controllers serial 1/0
M8T-232: show controller:
PAS unit 0, subunit 0, f/w version 1-19, Rev id 0x2800001, version 2
idb = 0x60942688, ds = 0x608A6570, ssb=0x608C6CF0
Clock mux=0x0, ucmd_ctrl=0x1C, port_status=0xC
maxdgram=1524, bufpool=32Kb, 64 particles
DCD=up DSR=up DTR=down RTS=down CTS=up
line state: down
cable type: RS232 DCE cable, received clockrate 123984
[display text omitted]
Following is an example of the show controllers cbus command that shows a VIP interface port (2/1/0)
that has a DTE cable attached:
Router# show controllers cbus
slot2: VIP2, hw 2.2, sw 21.40, ccb 5800FFA0, cmdq 480000C0, vps 8192
software loaded from flash slot0:muck/amcrae/vip2_21-40.mxt
FLASH ROM version 255.255
Mueslix Serial(8), HW Revision 0x1, FW Revision 1.20
Serial2/1/0, applique is RS232 DTE
gfreeq 48000140, lfreeq 480001B0 (1536 bytes), throttled 0
rxlo 4, rxhi 90, rxcurr 0, maxrxcurr 0
txq 48001A80, txacc 48001A82 (value 58), txlimit 58
[display text omitted]
To change the mode of a port online, use software commands to shut down the interface, replace the
compact serial cable, restart the interface, and (if necessary) reconfigure the port for the new interface.
At system startup or restart, the system polls the interfaces and determines the electrical interface type
of each port (according to the type of compact serial cable attached). However, the system does not
necessarily repoll an interface when you change the adapter cable online. To ensure that the system
recognizes the new interface type, shut down and re enable the interface after changing the cable.
If you are replacing a cable with a cable that has the same mode, these steps are not necessary (simply
replace the cable without interrupting operation).
