Right on Don.

73,

Fred KE7X


________________________________
From: elecraft-boun...@mailman.qth.net <elecraft-boun...@mailman.qth.net> on 
behalf of Don Wilhelm <donw...@embarqmail.com>
Sent: Friday, March 2, 2018 5:19 PM
To: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Advice needed: Remote Station Enhancement

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.

73,
Don W3FPR

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
>> amateur).
> 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
> interface.
>
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