RS-232 (was: Re: DEC VT05 with OS/8 -- basic system rebuild?) - test-drb@ccmp.vtda.org

20 May 2009

Dave McGuire <mcguire at neurotica.com> wrote:

...
  On May 19, 2009, at 3:21 AM, Johnny Billquist wrote:
    In general, when talking about DEC equipment, the
answer to that  
 question is *always* no, for the simple fact that DEC didn't do  
 hardware flow control. Hardware flow control is actually against  
 the RS-232 spec, and DEC didn't abuse standards (unlike most  
 other companies).  This reminds me of a comment I made about the HP82164 (HPIL to 

 RS232 interface). That thing follows the RS232 standard to the  
 letter (for example, it correctly handles the cotnrol lines in  
 half duplex mode). It's just a pity that nobody else does :-).  
 Getting it to work with some RS232 devices is 'interesting'..  Yeah. HP was
actually the other company that actually seemed to  
 read the standard. I don't know of anyone else than DEC and HP that  
 even tried to actually follow the specs.
 One could only wish companies had. Everything would have been soo  
 much easier in that case. Now almost everyone is confused when it  
 comes to serial communication, and it's not because it actually is  
 difficult, but people have just become so confused because they  
 think it works one way just because the equipment they have do it  
 that way, and when coming to any other equipment, nothing works the  
 same way they are used to.  
    Well, you've got to admit that things would've been a whole lot  
 easier if it weren't for the whole DTE/DCE fiasco. 
While I must admit that I don't understand the point of having a 
separate DTE and DCE, if companies had just followed the specs, it 
wouldn't have been a problem anyway.
All DTEs male, and all DCEs female. Female to female cable, always 
crossed (same with male to male, not that I'd expect many to hook a DCS 
to a DCS, but anyway), and male to female cables always straight. How 
easy it would have been.
And modem signaling are just signalling between a DTE and DCE, for 
various situations.

But they could have defined just everything as DTEs, and made modems and 
similar stuff really invisible, like cable extensions instead. Maybe 
that would have made it easier for companies to get it right.

	Johnny

-- 
Johnny Billquist                  || "I'm on a bus
                                   ||  on a psychedelic trip
email: bqt at softjar.se             ||  Reading murder books
pdp is alive!                     ||  tryin' to stay hip" - B. Idol