Pretty much all Denon receivers use roughly the same IR codes (some later models use Kaseikyo as well as Sharp codes - I'd think the 687 only uses Sharp codes), although the names of inputs can change slightly. I can't find a doc specifically for the 687, but it probably follows the pattern on the 688, so I suggest you get the following PDF:

[Link: usa.denon.com]

Then have a read of

[Link: remotecentral.com]

and

[Link: remotecentral.com]