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From: jrd@cc.usu.edu
Newsgroups: comp.sys.ibm.pc.misc
Subject: Re: DSZ upload problem at 19200 baud - flow control?
Message-ID: <1991Mar2.151246.46973@cc.usu.edu>
Date: 2 Mar 91 21:12:46 GMT
References: <7264.27cd2589@cc.curtin.edu.au>
Organization: ÿÿÿÿ
Lines: 42

In article <7264.27cd2589@cc.curtin.edu.au>, Gumley_LE@cc.curtin.edu.au (Liam Gumley) writes:
> I am using DSZ.COM on a 386-AT to upload and download files from a VAX/VMS
> system that has RZ and SZ.  The transfers are done over a direct serial link
> (i.e. no modem, just cable.)
> 
> Previously I have been able to do both uploads and downloads at 9600 baud with
> no problems.  A recent line upgrade now allows me to run my PC (as a terminal)
> with Kermit at 19200 baud.
> 
> The problem is that while SZ(VAX) -> DSZ(PC) still works fine at 19200 baud,
> DSZ(PC) -> RZ(VAX) now gets all kinds of errors at 19200 baud.
> I have set the speed correctly for DSZ in each case.
> 
> The errors start with the first 1024 bytes of data transmitted, and DSZ says
> Got ZRPOS.
> 
> Okay, I looked in DSZ.DOC, and ZCOMMDOC for a solution.  They indicated that
> it was probably a flow control problem.  So I tried DSZ receive with
> handshake on, off, slow, both, and none of them worked - I still got the
> same errors.  Now it must be that the VAX cannot respond quickly enough to
> the PC at 19200 baud.  I have tried a couple of different versions of the
> software on both the VAX and the PC and get the same errors every time.
> 
> Can anyone offer some advice? (apart from going back to 9600 baud....)
> 
> Cheers,
> Liam.

	The problem may likely be the serial board in the VAX. That is, some
have a (too) wide tolerance on the speed at 19,200 b/s and the receiving end
can be on the other side of the tolerance. In addition, cable length plays
a major role as the speed increases; I'd stay closer than 250 feet at 19,200.
On top of that the UART in the PC enters the picture if it is an 8250B (the
slow slow version). To diagnose the problem further use MS-DOS Kermit on the
PC and either LOG PACKET or SET DEBUG ON, or both, to see what arrives and
departs. Then I'd vary the packet length going to the VAX to sense interrupt
latency effects on the VAX.
	Joe D. 
> -- 
> tgumleyle@cc.curtin.edu.au
> #Liam E. Gumley, Department of Applied Physics, Curtin University of Technology#
> #Perth, Western Australia.   >>>All opinions expressed are exclusively mine.<<<#