External Keyboards (for SX-64 and 128D)

What exactly is the keyboard interface for Commodore's detached keyboards? Did they essentially take the keyboard out, give it its own case, and lengthen the cable? Or is there something more devious going on?

I'm a bit like that kid on Toy Story, the one that liked to push the limits, so to speak, on the interchangeability of various toy parts.  I seem to always be coming up with passible ways do do strange things with my 64.  The two external keyboards of the 128D and the SX-64 provide one of these possibilities.

These days, keyboards that are separate from the computer, connected via a wire, are the norm.  (Well, we'll just overlook those little toys they call nettops, or laptbooks, or whatever.)  All for the better if you ask me, since I find the most ergonomic place for a keyboard is on my lap, as low as possible.  I have pictured myself using the C64 in lap-top fashion, but I think that the things I'd like to keep plugged in to it would make that less than comfortable.  I also recall those summer days working with my C64, the sweat nearly dripping from my hands because of the heat from the motherboard escaping upward.

Hmmm... I think I've digressed or something.

When I first heard of the 128D, having already played with keyboard scanning, I instantly wondered how the keyboard was interfaced.  Did they really run 16+ wires directly from the CIAs to the keys?  Or did they use a serial connection like IBM PCs had already been using?  It was many years later that I actually learned enough about the 128D to know that it used a DB-25 connector, as used by the early RS-232 devices and the PC parallel port.  Was this an indication that Commodore went with an RS-232 connection?

At some point I realized that the SX-64 used the same connector, for the same purpose.  Did the engineers use the same design for both systems?  I really doubt that the designers had any intention to make the two keyboards interchangeable, but would they have any motivation to re-invent the wheel either?

Guess I'll just have to try it out.  There may be a slight chance of damaging the hardware, I suppose, if differeing pin assignments happened to resulted in connecting two outputs together;  but I don't know too much about what the chips can safely handle.  If 6526 chips grew on trees I'd just plug and play, but they don't.  So I'll probably use a DB25 breakout box and make all the connections using resistors.

[Edit: 2010-09-08]
BTW, I realize this would be pretty easy to figure out by researching documentation.  But experimenting is more fun.  =)