1.\" Copyright (c) 1985, 1991 Regents of the University of California. 2.\" All rights reserved. 3.\" 4.\" %sccs.include.redist.man% 5.\" 6.\" @(#)dhu.4 6.3 (Berkeley) 03/27/91 7.\" 8.Dd 9.Dt DHU 4 vax 10.Os BSD 4.3 11.Sh NAME 12.Nm dhu 13.Nd 14.Tn DHU-11 15communications multiplexer 16.Sh SYNOPSIS 17.Cd "device dhu0 at uba0 csr 0160440 vector dhurint dhuxint" 18.Sh DESCRIPTION 19A 20.Tn DHU-11 21provides 16 communication lines. 22.Pp 23An optional argument 24.Ar flags 25may be supplied with the device specification 26in the config file indicating 27that the line corresponding to 28bit number 29.Ar i 30is not properly 31connected, and should be treated as hard-wired with carrier 32always present. Thus specifying 33.Ql flags 0x0004 34for 35.Li dhu0 36would cause line 37.Pa ttyS2 38to be treated in this way. 39.Pp 40Normal I/O 41control parameters for individual lines are managed by 42.Xr ioctl 2 43calls. 44Individual 45.Tn DHU-11 46lines may be configured to run at any of 13 speeds 47(50, 200 and 38400 baud are not available); 48the speed may be set via 49.Xr getty 8 50or 51.Xr stty 1 52or may be communicated by other programs which 53utilize 54.Xr ioctl 55such as 56.Xr ifcongif 8 , 57see 58.Xr tty 4 . 59.Pp 60The 61.Tn DHU-11 62driver normally uses input silos 63and delays receiver interrupts by 20 milliseconds 64rather than taking an interrupt on each input character. 65.Sh FILES 66.Bl -tag -width /dev/tty[S-Z][0-9a-f]xx -compact 67.It Pa /dev/tty[S-Z][0-9a-f] 68.El 69.Sh DIAGNOSTICS 70.Bl -diag 71.It dhu(%d,%d): NXM fault. 72No response from 73.Tn UNIBUS 74on a 75.Tn DMA 76transfer 77within a timeout period. This is often followed by a 78.Tn UNIBUS 79adapter 80error. This occurs most frequently when the 81.Tn UNIBUS 82is heavily loaded 83and when devices which hog the bus (such as 84.Tn RK07 Ns s ) 85are present. 86It is not serious. 87.Pp 88.It dhu%d: silo overflow. 89The character input silo overflowed 90before it could be serviced. This can happen if a hard error occurs 91when the 92.Tn CPU 93is running with elevated priority, as the system may 94then print a message on the console with interrupts disabled. 95.El 96.Sh NOTES 97The driver currently does not make full use of the hardware 98capabilities of the 99.Tn DHU-11 , 100for dealing with 101.Tn XON/XOFF 102flow-control or hard-wired 103lines for example. 104.Pp 105Although the devices are not the same, a 106.Tn DHU-11 107can convince the 108.Tn DH-11 109autoconfiguration code that it is a 110.Tn DH-11 . 111.Pp 112The 4 40-way cables are a pain. 113.Sh SEE ALSO 114.Xr tty 4 115.Sh HISTORY 116The 117.Nm 118driver appeared in 119.Bx 4.3 . 120