Nak changer protocol (ACC, DSP-SEL, and CDCRST) - diyAudio
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Old 26th January 2009, 07:28 AM   #1
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Location: Bay Area
Default Nak changer protocol (ACC, DSP-SEL, and CDCRST)

Hello Everyone,

This is my goal:
I want to connect multiple (Nakamichi brand) CD changers to my Nakamichi CD player. There is no source select adapter for this like for modern Sony Unilink devices.

I figured I could do something like wire up everything in parallel except ACC (inser appropriate pin name here) which I'd wire to a selector switch, allowing me to manually and externally select a desired CD changer. The CD changer the radio would then interface with as normal.

I am not trying to change the protocol clock or data in any way.

What I don't know is how the "handshake" happens between the Nakamichi player and changer. Here is what I assume happens:

-Plug everything in together and power up the CD player.
-Player sends a "who's here?" message, and the changer responds. "I'm here!"
-Turn player on, and and cd player says "get ready CDC, we are gonna play"
-the rest of cd changer activity commences.

Now, it looks like there are three comm lines nakamichi uses to figure this out. ACC, DSP-SEL, and CDCRST.

What I don't know is what each line does persay, whether it's a simple 12v on, gnd off kind of signal, and if interrupting any of the three will screw up the initial handshake.

I'm worried if I interrupt a line, the CD player will say "hey, you arent the cd changer I did a handshake with when I first powered up so long ago! I'm going into an error state!"

ACC seems easy. Figure it mimics the ACC input on the radio.

But does anyone know precisely what DSP-SEL and CDCRST do? Can I just splice three cables together, run DSP-SEL into a 3 position selector switch, and hook up three changers to my nakamichi and select from them willy nilly?
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Old 26th January 2009, 07:40 AM   #2
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Join Date: Apr 2005
Location: Bay Area
I find this interesting:

http://www.mictronics.de/?page=cdc_proto

check out the kenwood protocol. We know the early 90's protocol matches the Nak, and that this protocol is not the same. However, we do not know if the same handshake structure is in place, if only the data/clock pins change.

I only see 10 wires on the Nak DIN cable, leaving the three audio lines to complete the 13 pin connector. And not surprisingly, though the protocol has been updated, the audio lines on the kenwood connector match pin for pin the nakamichi TB concerning breaking out audio lines from kenwood changers.

Why I mention this is because this kenwood protocol has more pin detail. In particular, a CH-CON pin that makes me wonder if it matches DSP-SEL, matching output reset, explaining that is communication FROM the player TO the changer, and only find ACC missing.

seems like another clue that someone who looks at these things might have more conceptual insight into. any thoughts?
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