Hook the Keydown Event in the TinyMCE Post Editor

I would like to hook the keydown event in the TinyMCE Editor on the edit post admin page. I managed to hook the HTML content editor using the following code:

jQuery('#content').keydown(function(){
    alert("keydown")
});

Here is my failed attempt at hooking the TinyMCE editor. The problem is that the editor hasn’t been init yet so the variable ed is undefined.

var ed = tinyMCE.getInstanceById('tinymce');
ed.onChange.add(function(ed, l) {
    alert("keydown");
});

Any help would be much appreciated!

the TinyMCE Editor has its own keydown event handler and its hooked to a function on initiation so to do that you can create a tinymce plugin or use the wordpress initiation of it with tiny_mce_before_init hook like this:

add_filter( 'tiny_mce_before_init', 'wpse24113_tiny_mce_before_init' );
function wpse24113_tiny_mce_before_init( $initArray )
{
    $initArray['setup'] = <<<JS
[function(ed) {
    ed.onKeyDown.add(function(ed, e) {
        //your function goes here
        console.debug('Key down event: ' + e.keyCode);
    });

}][0]
JS;
    return $initArray;
}