Reply To: Controlling a Beomaster 6500 via the TV/Aux Datalink’86 pin

[TK]

Yes, I have one of his BeoTooth devices, and it’s very well made.

I’ll explain it this way: The beocord is able to transmit lots of information about it’s current state over datalink: what track it’s on, what side of the tape it’s playing, how many seconds it’s been running, how loud the recording is, etc. It’s a very “chatty” component.  In the example above, it’s transmitting CassetteInfo, TrackNumber, and Counter over Datalink for the Beomaster to display. Most Datalink 80 messages are 1 byte in length (eight 1’s and/or 0’s in sequence, in specific combinations) , but a few status messages are longer, because more information needs to be passed then can be done in a single byte.  Fore example, when the Beomaster sees the incoming. code for “TrackNumber” it knows that the next 5 bytes it receives will include which track it should display on the remote. HOWEVER! of the next five bytes it is expecting, only the last byte received is ever used (AFAIK) for this particular status command, and of that last byte, only a portion of it is used. So the first four bytes of the message could have been jibberish, but the original writers of Datalink 80 apparently decided to send “00000111”, which is translated as either “UNKN” or “14+” on your B&O display. But in practice it really doesn’t matter what is sent – the first 4 bytes of data is not used for anything, AFAIK.  They could have chosen to send something else if they’d wanted to.

The ‘UNKN’ label is basically the English label Ive assigned for the sequence of bits ‘1111’, or the Hex letter ‘F’.  which also represents the number 15 in computer-speak.  It’s the largest number that can be represented using 4 bits.  This is the primary reason why most older B&O systems only count tracks up to 14. On any higher numbered track, it will show as “14+” which is signifies “Track 15 or higher”, and also “Unknown Track Number”.  AKA “I can’t count any higher than that, because I’ve run out of digits”.

IF the last byte is also sent as “UNKN” (i.e five “UNKN” in a row), then the Beomaster knows that the beocord either does not know what track it’s. on, or the current track number is 15 or greater. The Beomaster  subsequently relays that information to a 2-way remote IR or the console panel, so the appropriate number is lit up. In the example above, the last number translates to a “10”, so solely the information in his last byte will cause the “10” to flash on an MCP panel.

Ironically,  the system already has a means to describe any track number between “0” and. “99999” easily, using the tape counter to transmit current track info.  In the example above, the Counter returns “07270”, which will display as “0727” on the MCP (I think- it might display “7270”, I’ll check later). Pilatomic has implemented this feature using the Status counter in his excellent adaptation.