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From: mcmahan@netcom.UUCP (Dave Mc Mahan)
Newsgroups: comp.sys.amiga.tech,comp.sys.amiga.hardware
Subject: Re: Help with serial printer
Message-ID: <12324@netcom.UUCP>
Date: 18 Jul 90 08:41:55 GMT
References: <31724@cup.portal.com>
Distribution: na
Organization: Dave McMahan @ NetCom Services
Lines: 35


 In a previous article, Sullivan@cup.portal.com (sullivan - segall) writes:
>
>My questions then are these:
>
>1.	How can you perform CTS/RTS handshaking when you can't 
>	determine the state of the CTS line?  (Especially when
>	there isn't any hardware support for handshaking protocols.)

Personally, I swear by my little LED 'blinky light tester'.  They plug
right inline with the RS-232 cable (assuming standard DB-25 connectors) and
let you observe from the real world what is going on while the program is
running.  They cost about $8-$12, depending on where you get it.  For those
in the Silicon Valley, you can get them at Fry's Electronics (Corner of
Oakmead and Lawrence Expressway in Sunnyvale) or Halted Specialties (Corner
of Central Expressway and Lawrence Expressway in Santa Clara).  There are
other places, I'm sure.  Lots of mail order places sell them, but they charge
too much.


>2.	Should CTS be asserted HIGH or LOW to allow data to be 
>	transmitted.

It should be 'asserted'.  Asserted (as I recall, but I may be wrong) means
a negative voltage level WRT signal ground (pin 7).  Why they made the
'asserted' state negative is beyond me, but that's the standard.  Of course,
your printer may think 'asserted' is positive voltage WRT signal ground, but
then I guess that's why the RS stands for "recommended standard".  How can
a standard only be recommended.  Either it is or it isn't.


>                           -Sullivan Segall


   -dave