This got me interested enough to drag out my Tech Ref copy,
  says: Aug 1981 first edition (would not have expected first edition in 
'81?) refers to INS8250...

so we all predate the PC, the AppleII, the IMSA....
ho hum...
D

Rob Hamerling wrote:
> 
> Hello Aza,
> 
> Aza D. Oberman wrote:
> 
>> . . . . . . .   We spent quite a bit of time before
>> figuring out that the NS1645 UART on the original IBM serial and
>> serial/parallel port adapter card was wired in such a way that one 
>> could not
>> use software to turn off all the handshaking requirements for reading
>> RS-232.  It *had* to "see" a device out there before it would receive
>> anything.
> 
> 
> As far as I know the IBM-PC and later the PC-XT were standard delivered 
> with a monochrome display/printer adapter. An 'Asynchronous 
> Communications Adapter' was an option.  This adapter was equiped with an 
> NS8250 and a 25-pin subD connector (IBM Tech Ref April 1984).
> 
> The combined asyn/printer adapter came with the PC/AT, and this adapter 
> was equiped with an NS16450 and a 9-pin subD connector (IBM Tech Ref for 
> the PC/AT, September 1985). This is probably the one you are referring 
> to?  I have still such an adapter in use on an old Pentium I use for 
> experiments. Maybe it is a later version, but I have never experienced 
> problems with flow control lines.
> 
> 
>> Three wire (RX, TX, & Common) RS-232 is certainly convenient, but I still
>> question if it is a good practice to not at least strap the handshaking
>> lines when designing a RS-232 device. 
> 
> 
> I agree. When I build a PIC-based device with UART I either implement 
> CTS/RTS handshaking or use loop-backs with a current limiting resistor.
> 
> [Ironically, I believe the "RS" in
> 
>> "RS-232" stands for "Recommended Standard" -- makes one wonder what the
>> official one  is...]
> 
> 
> Isn't it an EIA or IEEE standard today?
> 
> Regards, Rob.
> 

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