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From: okamoto@hpcc01.HP.COM (Jeff Okamoto)
Newsgroups: comp.sys.mac.comm
Subject: Problems using ZTerm and sz/rz
Message-ID: <1970001@hpcc01.HP.COM>
Date: 21 Mar 91 18:33:44 GMT
Organization: Cha Cha Maru
Lines: 42

I'm having a strange problem with ZMODEM file transfers and am
wondering if anyone can help.

I'm using ZTerm 0.85 on a Mac II running 6.0.5 with a fair number of
INIT's.  I have a Racal-Vadic 9600 baud modem which speaks V.32
connected to the modem port.  On the Unix machine at work, I'm using
sz version 3.03 5-09-89 and rz version 3.00 4-19-89.  The bank of
modems that eventually connect to the Unix machine are connected
via a dialback system.

The symptom: when uploading both text and binary files, I will get
ZRPOS errors which will eventually cause the file transfer to fail.
For a while, these consistently occurred after 1024 bytes had been
transferred, but recently, the transfer went as far as 20K before
the ZRPOS's started.  The weird part is that downloading text and
binary files has never failed (yet).

I have tried forcing the mode of the transfer with options to rz and
options in ZTerm.  I believe I have also tried escaping control
characters (-e option to rz).  I have tried cutting down the packet
size in ZTerm to 256 characters.  None of these seems to make any
difference.

The ROM in my modem WAS recently upgraded, and the time of the change
vaguely corresponds to the difficulties I'm having.  I do not believe
any of the non-volatile settings were changed.  I also don't quite
understand why, if this is the true cause of my problem, I should
still be able to download, but not upload.

To add to the craziness, just last night, I managed to upload a small
binary file and it came through okay.

My first question is: what would cause rz to begin issuing ZRPOS's?
My second question is: why is this happening?

The EC (error correction) LED on the modem is on while I am connected.
I believe the modems are using MNP5.  The cable connecting my modem to
the Mac is a standard cable (ie, it isn't a hardware handshake-capable
cable).

I would appreciate any help or suggestions that you might have to
offer.