Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!wuarchive!waikato.ac.nz!comp.vuw.ac.nz!gp.co.nz!zl2tnm!don
From: don@zl2tnm.gp.co.nz (Don Stokes)
Newsgroups: comp.sys.dec
Subject: Re: RE: KA820 processor's serial lines, what use?
Message-ID: <3B9c24w163w@zl2tnm.gp.co.nz>
Date: 3 May 91 22:48:49 GMT
References: <22334.281ea112@cluster@ukc.ac.uk>
Organization: Computer Archaeologists
Lines: 40

cur022%cluster@ukc.ac.uk (Bob Eager) writes:

> In article <26APR91.19245964@toron.waisman.wisc.edu>, karcher@toron.waisman.w
> > These are real live serial ports you can do anything you want with. The
> 
> No modem control, though. And I believe that > 1200 bps is not supported
> (although I run one at 9600). I suspect that if you used all of them, you
> might have some slowdown problems in the CPU; I think there is a lot of
> microcode involved.

I've run one at 19.2K, but it locked up on me after a bit of abuse (it
may have been fixable and unrelated to the port type; I only tried it
once and that was in the middle of some crisis or other).  It did work,
ie the UARTs and software know what you're talking about.

Re microcode, yes I believe so -- these are basically the same sorts of
ports as OPA0 on any other VAX, ie addressed using MTPR and MFPR (move
to/from processor register) instructions rather than memory mapped I/O.
As such, they're character oriented (rather like the dreaded DL-11), and
tend to suck on the CPU a bit.  Flow control is handled in software, so
if you sling a large chunk of data at them from the attached device at a
high speed, it's almost guaranteed to (a) drop half of it on the floor,
and (b) choke the CPU (I'm reasonably sure this was what caused the
lockup I mentioned above). Running a couple of terminals off them should
be OK however.

> I also believe that VMS doesn't configure them if you have other serial
> ports attached.

No, it doesn't.  I posted the necessary SYSGEN incantations earlier.

With regard to the fellow who asked if the ports have a DB25
distribution panel:  I'm not sure.  As I said, all VAXes have a console
port, so that at least will have a DB25 present, but the other three
ports may not.  Without digging the manual out or opening the machine up
and looking, I couldn't say -- I'm at home and the machine is at work.

Don Stokes, ZL2TNM  /  /                             don@zl2tnm.gp.co.nz (home)
Systems Programmer /GP/ GP PRINT LIMITED  Wellington,       don@gp.co.nz (work)
__________________/  / ----------------   New_Zealand__________________________