cracking the code

My camera can identify the lens in use and provide useful EXIF data such as settings for the exposure and the version of the lens used; to enable this the lens needs to be coded (called 6-bit), only one of my lenses is coded.  If the lens isn't coded you can use a manual setting to detect the lens and match it to an equivalent coded lens.  The detection is via a sensor window on the camera lens mount which picks up the code from the lens mount and sets the camera accordingly.  I couldn't set my non-coded lens to a manual setting because the menu option was 'greyed out', and couldn't fathom it out!  After conversations with friends who have similar cameras, it was simply because the sensor and lens mount needed cleaning. Two minutes of cleaning later and the camera sensor now recognises my non-coded lens and sets equivalent EXIF information; code cracked!