1.\" Copyright (c) 1990, 1991 The Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" This code is derived from software contributed to Berkeley by 5.\" the Systems Programming Group of the University of Utah Computer 6.\" Science Department. 7.\" %sccs.include.redist.man% 8.\" 9.\" @(#)dcm.4 5.2 (Berkeley) 03/27/91 10.\" 11.Dd 12.Dt DCM 4 hp300 13.Os 14.Sh NAME 15.Nm dcm 16.Nd 17.Tn HP 1898642A communications multiplexer 19.Sh SYNOPSIS 20.Cd "device dcm0 at scode? flags 0xe" 21.Sh DESCRIPTION 22The 23.Tn 98642A 24is a four port 25.Tn EIA 26.Tn RS-232C 27.Pf ( Tn CCITT 28.Tn V.28 ) 29communications 30multiplexer. The 31.Tn 98642A 32has three direct-connect ports and one port with 33full modem control. 34.Pp 35Input and output for each line may set to one of following baud rates; 3650, 75, 110, 134.5, 150, 300, 600, 1200, 1800, 2400, 4800, 379600, 19200, 38400. 38.Pp 39.Ar Flags 40is usually specified as 0xe since 3 of the 4 ports (1-3) do not support 41modem control and should be treated as hard-wired with carrier always present. 42If port 0 does not have the need for modem control then flags can be specified 43as 44.Ql 0xf . 45.Pp 46Each port on the 47.Tn 98642A 48has a 128 byte input silo and a 16 byte output silo. 49Interrupts happen on a per character basis unless the interrupt 50rate for the card reaches 70 interrupts per second at which time the 51driver changes to a 16.7ms (60 interrupts per second) polling scheme until 52the interrupt rate drops. 53.Sh FILES 54.Bl -tag -width /dev/tty0[0-9a-f] -compact 55.It Pa /dev/tty0[0-9a-f] 56.El 57.Sh DIAGNOSTICS 58.Bl -diag 59.It dcm%d port%d: silo overflow 60Input Silo has overflowed and incoming data 61has been lost. 62.Pp 63.It dcm%d port%d: uart overflow 64The 3 character buffer in the uart has 65overflowed. 66.El 67.Sh SEE ALSO 68.Xr tty 4 69.Sh HISTORY 70The 71.Nm 72driver 73.Ud 74.Sh BUGS 75Total throughput per card, all ports together, is limited to 76800 bits per 76second continuous input rate. 77