All firmware updates are handled by the Internet Service Provider.  Motorola provides your Internet Service Provider with the firmware update.  Once it passes all their testing, they push it onto the customer's cable modem via the coaxial cable. 

There is no way for an end-user to update cable modem firmware manually.  To make sure you have the latest firmware update from us:

Power off your cable modem for 15 seconds, and then turn it on again.  As it reboots, your modem will check if it's running the latest code from your service provider. 

If your modem does not have the latest code/firmware, it will download the latest version.