110 lines
3.8 KiB
Groff
110 lines
3.8 KiB
Groff
.\"
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.\" Copyright (c) 1996 Jonathan Stone.
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.\" All rights reserved.
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.\"
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.\" Redistribution and use in source and binary forms, with or without
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.\" modification, are permitted provided that the following conditions
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.\" are met:
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.\" 1. Redistributions of source code must retain the above copyright
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.\" notice, this list of conditions and the following disclaimer.
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.\" 2. Redistributions in binary form must reproduce the above copyright
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.\" notice, this list of conditions and the following disclaimer in the
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.\" documentation and/or other materials provided with the distribution.
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.\" 3. All advertising materials mentioning features or use of this software
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.\" must display the following acknowledgement:
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.\" This product includes software developed by Jonathan Stone.
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.\" 4. The name of the author may not be used to endorse or promote products
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.\" derived from this software without specific prior written permission
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.\"
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.\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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.\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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.\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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.\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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.\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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.\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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.\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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.\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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.\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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.\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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.\"
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.\" $NetBSD: dc.4,v 1.10 2001/09/21 09:11:46 gmcgarry Exp $
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.\"
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.Dd February 20, 1998
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.Dt DC 4 pmax
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.Os
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.Sh NAME
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.Nm dc
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.Nd
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dc659, dc7085 DZ11-on-a-chip serial communications interface
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.Sh SYNOPSIS
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.Cd "dc* at ibus0 addr ?"
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.Sh DESCRIPTION
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The
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.Nm
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driver provides support for Digital's dc7085 four-port serial
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communications chip.
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The
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.Nm dc
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driver supports dc7085 hardware found on the DECstation 2100, 3100,
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5100, the optional expansion devices on the 5100, and the DECstation
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5000/200.
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.Pp
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The
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.Nm
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device is in essence a single-chip clone of the DZ-11.
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The DZ-11 hardware design severely constrains performance because
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it has one small input silo that is shared across all ports.
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The
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.Nm dc
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hardware does not interrupt on modem transitions; instead,
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they must be detected by polling the device.
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Only two ports on a baseboard
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.Nm dc
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device have any modem control signals;
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the other two ports are wired for a keyboard and mouse.
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.Sh SEE ALSO
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.Xr ibus 4 ,
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.Xr intro 4
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.Sh BUGS
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On some implementations (e.g. DECstation 3100), the hardware does not
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bring out modem flow-control signals (RTS/CTS) to the bulkhead;
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only modem carrier transition are provided.
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This is adequate for
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.Ux
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dialin and dialout detection, but without hardware flow control, the
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.Nm
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device is prone to input silo overruns when used for serial-line
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protocols at high speed.
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The DECstation 5000/200
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.Nm
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hardware provides full modem control on both bulkhead RS-232 ports
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and is thus less prone to input silo overrun.
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.Pp
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The 19200 speed on all
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.Nm
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devices is actually implemented as 19800,
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presumably for bug-compatibility with the original DZ-11.
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This is a hardware "feature" and cannot be corrected in software.
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Many serial devices at 19200 fail to interoperate with the
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.Nm
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at its 19800 speed setting.
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.Pp
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The DECstation 5000/200 can set a bit in the system register to allow the
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.Nm
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to run at 38400, but this applies to all four ports and disables
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the 19200 speed on all four ports.
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This feature is not currently supported.
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.Pp
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The
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.Nm
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driver should be merged into a single driver supporting the original
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DZ-11, DZ-32, and Qbus DZV-11 and DZQ-11 clones.
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.Sh HISTORY
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The
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.Nm
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driver
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first appeared in
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.Bx 4.4 .
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This manual page first appeared in
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.Nx 1.2 .
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