Path: utzoo!mnetor!uunet!husc6!bbn!mit-eddie!uw-beaver!uw-june!uw-entropy!dataio!pilchuck!del
From: del@Data-IO.COM (Erik Lindberg)
Newsgroups: comp.sys.ibm.pc
Subject: Re: Problem redirecting to COM1 in DOS 3.3
Message-ID: <884@pilchuck.Data-IO.COM>
Date: 5 May 88 20:53:40 GMT
References: <22210@teknowledge-vaxc.ARPA>
Reply-To: del@pilchuck.Data-IO.COM (Erik Lindberg)
Organization: Data I/O Corporation; Redmond, WA
Lines: 21
Keywords: DOS 3.3 COM1

In article <22210@teknowledge-vaxc.ARPA> 1dharvey@teknowledge-vaxc.ARPA (Doug Harvey) writes:
>  c:\>  echo logon > com1  [enter]
>
>	Write fault error writing device COM1
>	Abort, Retry, Ignore, Fail? 

The PC initializes the COM port to expect full handshake. You can change the
COM port initialization, as mentioned in another article, or you can make
a cable that supplies the appropriate signals. Assuming you only want a 3 wire
connections, and don't want to pay for the extra wires in your cable, make the
following connections at the PC end of the cable:

Connect pins 4&5 together.
Connect pins 5,8 and 20 together.

This will satisfy the UART and allow communications. You didn't have any
trouble with the internal modem because it is, of course, designed to work
with the PC internal BIOS.
-- 
del (Erik Lindberg) 
uw-beaver!tikal!pilchuck!del