SUMMARY: Does patch 100513-04 really fix RTS/CTS handshaking problem?

From: Gilbert E. Detillieux (
Date: Fri Aug 12 1994 - 13:25:17 CDT

In article <326d45$>, a few days ago, I wrote:
} I've got a V.32bis/V.42bis connected to the /dev/ttyb port on a Sun
} SPARCstation 2 running SunOS 4.1.3 with many patches applied. I've set
} things up so that the modem fixes the rate on the serial port at 38400, and
} have modified /etc/ttytab as follows:
} ttyb "/usr/etc/getty V32b" dialup on modem
} and I've added this entry to /etc/gettytab:
} V32b|V.32bis/V.42bis-Modem:\
} :sp#38400:ms=crtscts:hc:to#60:
} The setup works, and I had no problems with normal communication and with
} downloads from that port to my PC at home using Zmodem. The trouble was
} with uploads, since "crtscts" apparently is only implemented in one
} direction. I was under the impression there was a hardware limitation, but
} then I came across patch 100513-04. (I had been running with 100513-02
} before, but that didn't help with this problem.)
} I looked at the README files for both the -02 and -04 releases of this
} patch, and found this interesting addition:
} > BugID 1012954:
} > SunOS does not do RTS/CTS flow control for incoming datastreams, previously
} > Xon/Xoff flow control had to be used, (this has been fixed for CPU (zs_async)
} > serial ports only).
} >
} > BugID 1061643:
} > Synopsis: CTE zs driver gates reception on CD during hardware flow control
} With renewed optimism, I incorporated the patch, built a new kernel, and
} booted it. To my surprize, performance on zmodem uploads seems to be better
} than before. It's not flawless - I still get timeouts once in a while, but
} it seems better than it was with the -02 patch.
} The problem is downloads don't seem to work properly anymore. I used to be
} able to download without any errors, but I now get many timeouts and CRC
} errors with zmodem. These before-and-after tests were conducted minutes
} apart, with just the kernel reboot in between, so it's not due to a change
} in any other software or the port configuration.
} Anyone else have experiences to share regarding patch 100513-04? Have you
} been able to get things to work properly with it? Is the -04 release just
} plain broken, or is there just a configuration setting I missed? Should I
} junk the -04 release and go back to running -02? (Downloads are more
} important to me than uploads anyway.)
} Any insights or helpful suggestions would be most welcome. Thanks.

The answer I needed came from Apostolos Lytras <>, who
e-mailed me, and wrote:
> after applying the patches I also had to change eeprom settings, to use
> hardware handshaking. I don't know any more what the command was, but if
> you check out 'man eeprom' you'll find it

... and also later wrote:
> I am now at home, and here's what I set the eeprom to:
> ttya-mode=38400,8,n,1,h
> ttya-rts-dtr-off=false
> ttya-ignore-cd=false
> I am not sure whether getty overrides this, in fact I didn't change gettytab
> at all...

For me, the magic eeprom command I needed was:

        eeprom ttyb-mode=38400,8,n,1,h

(The h sets hardware, i.e. rts/cts, handshaking.)

After setting this, both uploads and downloads seem to work OK. I do still
get the occasional error (timeouts usually) on zmodem uploads, but the
performance is acceptable now. Downloads work like a charm again!

Thanks to Apostolos, and to all the others who replied or followed-up.

Gilbert E. Detillieux			Internet: <>
Dept. of Computer Science		 or  <>
University of Manitoba			Phone: (204)474-8161 (or Intercom 32)
Winnipeg, MB, CANADA  R3T 2N2		Fax:   (204)269-9178
     "The earth is like a tiny grain of sand, only much, much heavier."

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