1.\" $NetBSD: dcm.4,v 1.10 2017/02/17 22:24:46 christos Exp $ 2.\" 3.\" Copyright (c) 1990, 1991, 1993 4.\" The Regents of the University of California. All rights reserved. 5.\" 6.\" This code is derived from software contributed to Berkeley by 7.\" the Systems Programming Group of the University of Utah Computer 8.\" Science Department. 9.\" 10.\" Redistribution and use in source and binary forms, with or without 11.\" modification, are permitted provided that the following conditions 12.\" are met: 13.\" 1. Redistributions of source code must retain the above copyright 14.\" notice, this list of conditions and the following disclaimer. 15.\" 2. Redistributions in binary form must reproduce the above copyright 16.\" notice, this list of conditions and the following disclaimer in the 17.\" documentation and/or other materials provided with the distribution. 18.\" 3. Neither the name of the University nor the names of its contributors 19.\" may be used to endorse or promote products derived from this software 20.\" without specific prior written permission. 21.\" 22.\" THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 23.\" ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 24.\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 25.\" ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 26.\" FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 27.\" DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 28.\" OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 29.\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 30.\" LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 31.\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 32.\" SUCH DAMAGE. 33.\" 34.\" from: @(#)dcm.4 8.1 (Berkeley) 6/9/93 35.\" 36.Dd February 17, 2017 37.Dt DCM 4 hp300 38.Os 39.Sh NAME 40.Nm dcm 41.Nd 42.Tn HP98642A 43serial communications multiplexer 44.Sh SYNOPSIS 45.Cd "dcm* at dio? scode ? flags 0xe" 46.Sh DESCRIPTION 47The 48.Tn 98642A 49is a four port 50.Tn EIA 51.Tn RS-232C 52.Pf ( Tn CCITT 53.Tn V.28 ) 54communications 55multiplexer. The 56.Tn 98642A 57has three direct-connect ports and one port with 58full modem control. 59.Pp 60Input and output for each line may set to one of following baud rates; 6150, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 629600, 19200, 38400. 63.Pp 64.Ar Flags 65is usually specified as 0xe since 3 of the 4 ports (1-3) do not support 66modem control and should be treated as hard-wired with carrier always present. 67If port 0 does not have the need for modem control then flags can be specified 68as 69.Ql 0xf . 70.Pp 71Each port on the 72.Tn 98642A 73has a 128 byte input silo and a 16 byte output silo. 74Interrupts happen on a per character basis unless the interrupt 75rate for the card reaches 70 interrupts per second at which time the 76driver changes to a 16.7ms (60 interrupts per second) polling scheme until 77the interrupt rate drops. 78.Sh FILES 79.Bl -tag -width /dev/tty0[0-9a-f] -compact 80.It Pa /dev/tty0[0-9a-f] 81.El 82.Sh DIAGNOSTICS 83.Bl -diag 84.It dcm%d port%d: silo overflow 85Input Silo has overflowed and incoming data 86has been lost. 87.Pp 88.It dcm%d port%d: uart overflow 89The 3 character buffer in the UART has 90overflowed. 91.El 92.Sh SEE ALSO 93.Xr hp300/dio 4 , 94.Xr tty 4 95.Sh BUGS 96Total throughput per card, all ports together, is limited to 76800 bits per 97second continuous input rate. 98