projects / unix-history / blame
| Commit | Line | Data |
|---|---|---|
| 90a856fd KM |
1 | .\" Copyright (c) 1980 Regents of the University of California. |
| 2 | .\" All rights reserved. The Berkeley software License Agreement | |
| 3 | .\" specifies the terms and conditions for redistribution. | |
| 4 | .\" | |
| 0ac17531 | 5 | .\" @(#)dh.4 6.1 (Berkeley) %G% |
| 90a856fd | 6 | .\" |
| 0ac17531 | 7 | .TH DH 4 "" |
| 90a856fd KM |
8 | .UC 4 |
| 9 | .SH NAME | |
| a72e3b93 | 10 | dh \- DH-11/DM-11 communications multiplexer |
| 90a856fd | 11 | .SH SYNOPSIS |
| a72e3b93 | 12 | .B "device dh0 at uba0 csr 0160020 vector dhrint dhxint" |
| 90a856fd | 13 | .br |
| a72e3b93 | 14 | .B "device dm0 at uba0 csr 0170500 vector dmintr" |
| 90a856fd KM |
15 | .SH DESCRIPTION |
| 16 | A dh-11 provides 16 communication lines; dm-11's may be optionally | |
| 17 | paired with dh-11's to provide modem control for the lines. | |
| 18 | .PP | |
| 19 | Each line attached to the DH-11 communications multiplexer | |
| 20 | behaves as described in | |
| 21 | .IR tty (4). | |
| 22 | Input and output for each line may independently | |
| 23 | be set to run at any of 16 speeds; | |
| 24 | see | |
| 25 | .IR tty (4) | |
| 26 | for the encoding. | |
| 27 | .PP | |
| 28 | Bit | |
| 29 | .I i | |
| 30 | of flags may be specified for a dh to say that a line is not properly | |
| 31 | connected, and that the line should be treated as hard-wired with carrier | |
| 32 | always present. Thus specifying ``flags 0x0004'' in the specification of dh0 | |
| 33 | would cause line ttyh2 to be treated in this way. | |
| 34 | .PP | |
| a72e3b93 KM |
35 | The dh driver normally uses input silos |
| 36 | and polls for input at each clock tick (10 milliseconds) | |
| 37 | rather than taking an interrupt on each input character. | |
| 90a856fd KM |
38 | .SH FILES |
| 39 | /dev/tty[hi][0-9a-f] | |
| 40 | .br | |
| 41 | /dev/ttyd[0-9a-f] | |
| 42 | .SH "SEE ALSO" | |
| 43 | tty(4) | |
| 44 | .SH DIAGNOSTICS | |
| 45 | \fBdh%d: NXM\fR. No response from UNIBUS on a dma transfer | |
| 46 | within a timeout period. This is often followed by a UNIBUS adapter | |
| 47 | error. This occurs most frequently when the UNIBUS is heavily loaded | |
| 48 | and when devices which hog the bus (such as rk07's) are present. | |
| 49 | It is not serious. | |
| 50 | .PP | |
| a72e3b93 | 51 | \fBdh%d: silo overflow\fR. The character input silo overflowed |
| 90a856fd KM |
52 | before it could be serviced. This can happen if a hard error occurs |
| 53 | when the CPU is running with elevated priority, as the system will | |
| 54 | then print a message on the console with interrupts disabled. If the | |
| 55 | Berknet | |
| 90a856fd KM |
56 | is running on a |
| 57 | .I dh | |
| 58 | line at high speed (e.g. 9600 baud), there is only 1/15th of a second of | |
| 59 | buffering capacity in the silo, and overrun is possible. This may | |
| 60 | cause a few input characters to be lost to users and a network | |
| 61 | packet is likely to be corrupted, but the network will recover. | |
| 62 | It is not serious. |