[Elecraft] [acom-list] Re: Elecraft K3 and ACOM 2000A

[Don Wilhelm]

The confusion I am trying to clear is that more than one driver on an 
RS-232 line will not work properly and will result in erroneous data.

Multiple receivers are no problem.

Besides, you are quoting the standard for the receiver input.  In order 
to drive the long lines (as originally intended for RS-232), the driver 
output must be much greater.  Capacitance in the cable and resistance 
can distort the waveform and reduce the voltage.  Not usually a problem 
with short lines encountered in typical PC and ham radio setups, but is 
problematic when the line length gets long.
There is a difference between "it works", and "it works right all the time".

73,
Don W3FPR

On 9/15/2014 11:15 AM, Lynn W. Taylor, WB6UUT wrote:
> There is the formal standard, and there is the defacto standard.
>
> The formal standard says +3v for 1, -3v for 0, and that less than 3v 
> is undefined.
>
> The common driver chips (1488 and 1489) worked just fine with TTL 
> levels -- 5v being above +3, and 0v being close enough to -3v.
>
> I've never seen anything that required -3v for logic zero.
>
> -- Lynn
>
> On 9/15/2014 6:59 AM, Don Wilhelm wrote:
>> David,
>>
>> That is true the specification says that condition will not cause 
>> damage to compliant drivers and receivers, but if two drivers are 
>> placed on an RS-232 signal line, they will *not* work together and 
>> will result in corrupt data (assuming they are on the TXD or RXD 
>> signal lines).
>>
>> You are correct that damage may occur to non-compliant (but 
>> compatible) drivers and receivers.  The PC serial cards, USB to 
>> serial adapters, and most ham gear do not implement compliant RS-232 
>> interfaces.
>>
>> 73,
>> Don W3FPR
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to w3fpr at embarqmail.com
>