I believe that logic can quickly merge into the idea that "the first to introduce BCD Band Data" will "set the standard". I for one do not believe that is the best approach, and certainly not sufficient to 'set a standard', which may have serious flaws when extended beyond that manufacturer's realm.

The Yaesu method (I cannot call it a standard) will inter-operate with other Yaesu gear and 3rd party gear designed to inter-operate with it, but that does not constitute a "standard"

The "standard" for data communication has been established in the digital world for many, many years, and pre-dates the Yaesu system.

Drivers do not source voltage (they use open collector and open drain devices), and there is one pullup resistor at the end of the signal line - there may be multiple receivers monitoring the signal line, but there can be only one driver active at a time - which for a multiple driver situation means an external source of control is necessary for gating the drivers. I was working with those "rules" when designing computer console circuits for a IBM large system back in 1969, and the same principals had been devised since the advent of IBM SLT logic modules in the late 1950s.

So if anyone wants to apply "the first guy sets the standard", I think Yaesu was not the first, but they made the mistake of having the drivers source voltage. That is only practical for very short signal lines and a very limited number of receivers listening on the signal line(s).

Efforts to continue the "Yaesu method" will result in further confusion as amateur box to box communications develops further and more and more incorporates design principles previously applied to computer systems and communications lines. Even the IBM terminal communications plugged the "pullup" resistors at only one terminal (they were called line terminators) - at the end of the communications line. That is a long established principle that works even today if done right. What I am saying is that Yaesu did not "do it right" and creates limitations to expansion and the advancement of technology within the amateur community today.

So get out the cutters and remove the collector and drain resistors from the Yaesu drivers, and put pullup resistors only at the far end of the lines, and you can have the Yaesu "system" without any of the problems.

There are other systems that do allow multiple drivers on the same signalling line(s) - I2C is one example - whichever driver grabs the signalling first gets priority is a simplified version of the operation. Ethernet is another example, but in any of these systems, the protocol must define which driver gets priority. That requires a bit more sophistication than a simple driver on the communication line.

I believe the original K3 "did it right" to use open drain drivers on the band data lines - but succumbed to the hue and cry that it did not work with the various versions of the Yaesu system and Elecraft then added pullup resistors to the drivers. The result has been a bastardized "system" that in many cases requires the addition of steering diodes and/or the removal of pullup resistors from external devices to make it work right.


On 3/2/2018 6:17 PM, Joe Subich, W4TV wrote:

As far as older Yaesu transceivers are concerned, their design is proprietary and cannot be brought into the mold without serious
converters (which should frankly be easily constructed by the serious
Yaesu's transceivers were the *first* to use BCD "band data".  As such,
it should be incumbent on anyone using that interface to be electrically
compatible with Yaesu's interface (source +5/+12V for logic high, open
circuit for logic low).  Even the amateur DOS based logging software
that provided "band data" on a computer LPT port duplicated that

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