I haven't found the specific codes for the different character sets (uppercase, lowercase, numbers, Katakana, etc.). All I have found are the combination random access/ numbers /uppercase/ lowercase keys that are switched by toggle IR codes. Basically all keys on the RM-D7M remote. I'm guessing the codes sent out by the keyboard remote are 15-bit (these codes are 12-bit).
Hex Function Character #0780 - 1 F 1 #0781 - 2 G 2 #0782 - 3 H 3 #0783 - 4 I 4 #0784 - 5 J 5 #0785 - 6 K 6 #0786 - 7 L 7 #0787 - 8 M 8 #0788 - 9 N 9 #0789 - 10 O 0 #078A - >25 / #078F - Clear Del #0795 - Power #0796 - Eject #0798 - Display/Char #0799 - Scroll #079A - D Pre (not used on JE500) D #079B - D Rec (not used on JE500) E #079D - Continuous Play A #079E - Shuffle B #079F - Program C #07A0 - AMS/Track Reverse #07A1 - AMS/Track Forward #07A6 - Repeat ? #07A7 - A-B repeat ! #07A8 - Stop #07A9 - Pause #07AA - Play #07AB - Backward scan Cursor back #07AC - Forward scan Cursor fwd #07AD - Record #07B0 - T.Rec #07B3 - A.Space ( #07B4 - M.Scan ) #07B6 - Char (up/lowercase) #07B7 - Num (chars/numbers) #07BA - Clear #07BC - Name #07BD - Clear #07BF - Music Sync #07C0 - 11 P #07C1 - 12 Q #07C2 - 13 R #07C3 - 14 S #07C4 - 15 T #07C5 - 16 U #07C6 - 17 V #07C7 - 18 W #07C8 - 19 X #07C9 - 20 Y #07CA - 21 Z #07CB - 22 - #07CC - 23 spc #07CD - 24 . #07CE - 25 '