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Cisco Broadband Cable Command Reference Guide
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A P P E N D I X
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Using the ROM Monitor
This appendix describes the ROM monitor (ROMMON) that is used by the Cisco CMTS routers. The
Cisco CMTS runs the ROM monitor when it is initially powered on or reset, and the ROM monitor
determines what other software, such as a Cisco IOS boot helper image or software image, should be
loaded next.
Because the ROM monitor is in the permanent memory on the processor card, it is always available and
can help in troubleshooting possible hardware or software problems. It contains a small set of commands
that allow access to the router’s internal memory and other memory devices.
This appendix contains the following major sections:
•
Entering the ROM Monitor, page A-1
•
Command Conventions, page A-3
•
ROM Monitor Command Reference, page A-5
Caution
The ROM monitor should be used only by trained service technicians or under the direction of a
Cisco TAC engineer. Many of the commands available in the ROM monitor put the router in a diagnostic
mode or in a non-functional state. Do not enter any commands in the ROM monitor unless you
thoroughly understand their function and how to reverse their effects so that you can restore the router
to normal operations.
Entering the ROM Monitor
When the router initially powers on or reboots, the ROM monitor initializes the processor hardware and
boots the main Cisco IOS software. You can enter ROM monitor mode during the bootup sequence or
while the Cisco IOS software is running by using either the BREAK signal or by using the configuration
register. See the following sections for more information on each method.
Using the BREAK Signal
When the Cisco CMTS router is booting up, you can interrupt the start-up sequence and enter the ROM
monitor by sending the BREAK signal. If the Cisco IOS software image is already running, you can also
break into the ROM monitor by sending the BREAK signal. (Consult the documentation for your
terminal software for information on how to send the BREAK signal).
For example, the following shows the BREAK signal being sent to interrupt a router that is running
Cisco IOS software so as to enter ROM monitor mode.
