[comp.dcom.modems] Bit bit no parity vs 7 even

pat@grebyn.com (Pat Bahn) (08/11/89)

Hi
   THe system I dial up haswired modems for 8 bit no parity but
My PC gives me junk unless I use 7 Even.  I use procomm on a
compaq 386 with a hayes modem.  WHy do I get this behavior.
It even happens at work. the terminal server has a wired modem
going out at 8N but I have to set my terminal session to 7E.
The protocols are identical too aren't they?  ANy explanations
appreciated.
pat

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Pat @ grebyn.com  | If the human mind was simple enough to understand,
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scott@sequoia.UUCP (D. Scott Milton) (08/12/89)

In article <12259@grebyn.com> pat@grebyn.UUCP (Pat Bahn) writes:
>Hi
>   THe system I dial up haswired modems for 8 bit no parity but
>My PC gives me junk unless I use 7 Even.  I use procomm on a
>compaq 386 with a hayes modem.  WHy do I get this behavior.

	Check your AUTOEXEC.BAT file for the presence of the
DOS MODE statement. I strongly suspect you do not have one, as
the defaults are 7 data bits and even parity. If you include the
statement 'MODE COM1:9600,n,8' in your AUTOEXEC.CMD file, I think
that you will find that things will work properly.

edm@nwnexus.WA.COM (Ed Morin) (08/12/89)

Many times systems (especially Unix) will accept any parity because they
do not check it (i.e. just strip the bit), but *do* send out even parity.
With the 8th bit getting set to seemingly random 0's and 1's it will invoke
the characters defined in your terminal with the decimal values 128-255
which are often graphics, international, etc.  This will end up looking
like every few characters are garbaged in between normal looking stuff.
The fix you are using sounds like the best alternative...

-- 
Ed Morin
Northwest Nexus Inc.
"Unix Public Access for the Masses!"
edm@nwnexus.WA.COM

epsilon@wet.UUCP (Eric P. Scott) (08/14/89)

There are several places where things can go amiss.

Modems: before the days of "smart modems" this wasn't an issue;
10 bits went in for each character, the same 10 came out out the
other side.  Borrow another brand from a friend; if it suddenly
works right, we know who's to blame.

Software: some programs just don't work right; the worst offender
in my experience was BITCOM, the second worst was Procomm.  In
all fairness, this was some time ago, and I can't say which
versions had the problems.  The least effort fix was to hand the
user a copy of kermit.  Kermit always sets the serial port to
8-N-1 and does any needed parity hacking in software.

There could be a problem on the other end... but if they say it's
8-N-1, I'd tend to believe it.  7-E-1 should have gone away years
ago, sigh.

					-=EPS=-

GPWRDCS@gp.govt.nz (Don Stokes, GPO) (08/16/89)

In article <628@sequoia.UUCP>, scott@sequoia.UUCP (D. Scott Milton) writes:
> In article <12259@grebyn.com> pat@grebyn.UUCP (Pat Bahn) writes:
>>Hi
>>   THe system I dial up haswired modems for 8 bit no parity but
>>My PC gives me junk unless I use 7 Even.  I use procomm on a
>>compaq 386 with a hayes modem.  WHy do I get this behavior.
> 
> 	Check your AUTOEXEC.BAT file for the presence of the
> DOS MODE statement. I strongly suspect you do not have one, as
> the defaults are 7 data bits and even parity. If you include the
> statement 'MODE COM1:9600,n,8' in your AUTOEXEC.CMD file, I think
> that you will find that things will work properly.

Umm 'fraid not.  Procomm (like most other comms packages) completely 
ignores the mode setting.  *I* don't have a mode setting in my 
AUTOEXEC.BAT, and Procomm has no problems.  

I'm not sure what his/her (Pat for Patrick or Patricia?) problem is,
unless he/she is using something else in conjunction with Procomm, or an 
old version of Procomm that I haven't seen.  Note that it sounds like the 
modem is sending 7e1 into the computer, not the computer misinterpreting 
the parity.

Don Stokes, Systems Programmer    /  /   Domain:                  don@gp.govt.nz
Government Printing Office,      /GP/   PSImail:          PSI%0530147000028::DON
Wellington, New Zealand         /  /   Bang:    ...!uunet!vuwcomp!windy!gpwd!don
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