Serial Port Protocol MX2424/RC2424

[thedoogmeister]

GE fellow MX2424 users...

I'm needing to verify the remote control electrical interface between the MX and RC units. Before I open the RC unit to verify by chip inspection... does anyone know if the electrical spec is for EIA (RS) 232 or EIA (RS) 422. I know this may be confusing. I know these documents very well.

I am beginning the process of reverse engineering the data exchange so I can build the intercept bridge. Yes... I AM retired and have a bit of time on my hands to "get my hands dirty" again... unless anyone has actually found a manual covering the data structures and command set... which I've been unable to find. This is a best kept secret by TEAC/TASCAM.

Cheers

 

[mixerizer]

I wish I had info to help you with - I am looking at a similar project reverse-engineering the Alesis ADAT meter bridge format (a proprietary RS-422 format that, if unlocked, would allow the 32-channel RMB meter unit to see a new, useful life in the age of networked audio).

I think you are far more expert at the technical side but if I find anything that might be of help to you I will post here.

Good luck!

 

[thedoogmeister]

Thanks for responding... here's the truth about these specifications.. They define the SIGNALS, the VOLTAGE LEVELS, and the TIMING of the data changes. They do NOT define the PIN ASSIGNMENTS. The PIN ASSIGNMENTS are defined by the MANUFACTURER of the unit.

Cables usually do not "care" what the voltage is. As long as ALL PINs are wired on the connector. Usually... DBxxx MALE to DBxxx FEMALE: pin for pin.... i.e. 2 to 2, 3 to 3, etc
DBxxx MALE to DBxxx MALE or F to F... the signal pairs need to be swapped... i.e. 2 to 3, 3 to 2, etc.
This true for EIA-232.
Now... with EIA422... all bets are off... Pin assignments are NOT standardized. That's what makes my head spin!!!

 

[thedoogmeister]

Hey Gang,

I'm going to expand here a little bit about the 9-pin REMOTE connector on the RC-2424 for those who might want to MAKE an interconnect cable and some preliminary thoughts about the actual electrical specs.

As I look at the RC-2424 surface... I see that ONE RC unit can control up to SIX MX units (one at a time). That tells me that the REMOTE ports are RS-422 and most likely the Sony Pinout. This also tells me that the REMOTE is a DCE (Data Communication Equipment or Sender) and the MX units is a DTE (Data Terminal Equipment or Receiver). The pinout for the DE9 connector is (most likely): But remember this important fact: The RS-422 Specification does NOT include any pinout assignments. That assignment is defined by the equipment manufacturer!!! You MAY have to make a cable and test it with the equipment. More after I start my reverse engineering... unless someone else has already done that.

Pin 7- TX+
Pin 2- TX-
Pin 6 - Shield

Pin 3- RX+
Pin 8- RX-
Pin 4- Shield

Note the polarity swap between top row (pins 1-5) and bottom row (pins 6-9).
Comment about the Shield: RS422 uses a DIFFERENTIAL (pair) signal. With DIFFERENTIAL when TX+ is POSITIVE 5 volts, TX- is NEGATIVE is ZERO. This is the MARK (or 1) state of the data bit. When TX+ is NEGATIVE (ZERO) and TX- is POSITIVE (5Volts)... this is the SPACE (or 0) state of the data bit. The DIFFERENTIAL nature provides for NOISE IMMUNITY to the signal. Because of this feature... the SHIELD wire is NOT necessary. This is just like a BALANCED microphone signal.

So, if the pinout assignments ARE the Sony definition... the TX signals of the DCE device (RC-2424 MUST be connected to the RX signals of the DTE device (MX-2424). Observe POLARITY. Caveat... Tascam may have redefined the pinouts on the MX-2424 to allow for a STRAIGHT Thru cable. Do you see the confusion and frustration that can occur and need for experimentation.

I promise... more information in the future.