Introduction
How to download Cisco IOS firmware on AP
Resolution
If the wireless device has a firmware failure, you must reload the image file using either the Web browser interface or the 1100 and 1200 series Access Points (APs). Press and hold the Mode button for approximately 30 seconds. Refer to the Using the MODE Button:-
Step 1 
Disconnect power (the power jack for external power or the Ethernet cable for in-line power) from the access point.
Step 2 Press and hold the MODE button while you reconnect power to the access point.
Step 3 Hold the MODE button until the Status LED turns amber (approximately 1 to 2 seconds), and release the button.
Step 4 After the access point reboots, you must reconfigure the access point by using the Web-browser interface or the CLI.
Note:- The access point is configured with the factory default values including the IP address (set to receive an IP address using DHCP). The default username and password are Cisco, which is case-sensitive.
Section of Cisco IOS Software Configuration Guide for Cisco Aironet Access Points 12.3(7)JA: Troubleshooting. If the wireless device firmware is still fully operational, and you want to upgrade the firmware image, refer to the Using the Web Browser Interface section of the document:-
Follow these steps to delete the current configuration and return all wireless device settings to the factory defaults using the web browser interface:
Step 1 Open your Internet browser. You must use Microsoft Internet Explorer (version 5.x or later) or Netscape Navigator (version 4.x).
Step 2 Enter the wireless device's IP address in the browser address line and press Enter. An Enter Network Password screen appears.
Step 3 Enter your username in the User Name field.
Step 4 Enter the wireless device password in the Password field and press Enter. The Summary Status page appears.
Step 5 Click System Software and the System Software screen appears.
Step 6 Click System Configuration and the System Configuration screen appears.
Step 7 Click the Reset to Defaults button.
Note If the wireless device is configured with a static IP address, the IP address does not change.
Step 8 After the wireless device reboots, you must reconfigure the wireless device by using the Web-browser interface or the CLI. The default username and password are Cisco, which is case-sensitive.
However, you can use the Mode button when the AP has a corrupt firmware image on 350 series APs. You cannot use the Mode button to reload the image file, but you can use the Command Line Interface (CLI) through a Telnet or console port connection.
For more information, refer to these sections of the document:
You can obtain the wireless device image file from the Cisco.com software center by following these steps:
Step 1 Use your Internet browser to access the Cisco Software Center at the following URL:
http://www.cisco.com/cisco/software/navigator.html
Step 2 Find the wireless device firmware and utilities section and click on the link for the 350, 1100, or 1200 series wireless device.
Step 3 Double-click the latest firmware image file, such as c1100-k9w7-tar.122-11.JA for 1100 series access points or c1200-k9w7-tar.122-11.JA for 1200 series wireless devices.
Step 4 Download the image file to a directory on your PC hard drive.
Problem Type
Download
Upgrade
Products
Access point
Product OS
IOS
Reference Link
For more information on obtaining the TFTP server, refer to Obtaining TFTP Server Software