1DH(4) Kernel Interfaces Manual DH(4)
2
6 dh - DH-11/DM-11 communications multiplexer
7
9 /sys/conf/SYSTEM:
10 NDH dh_units # DH11; NDH is in units of boards (16 each)
11 NDM dm_units # DM11; NDM is in units of boards (16 each)
12 /etc/dtab:
14 #Name Unit# Addr Vector Br Handler(s) # Comments
15 dm ? 170500 310 4 dmintr # dm11 dh modem control
16 dh ? 160020 320 5 dhrint dhxint # dh11 terminal mux
17 major device number(s):
19 raw: 3
20 minor device encoding:
21 bits 0017 specify line on DH unit
22 bits 0060 specify DH unit
23 bit 0100 specify RTS/CTS (``hardware'') flowcontrol
24 bit 0200 specifies non-blocking open (``CD always on'')
25
27 A dh-11 provides 16 communication lines; dm-11's may be optionally
28 paired with dh-11's to provide modem control for the lines. If there
29 are fewer dm-11's than dh-11's, the dm-11's are assumed to be paired
30 with the first dm_units dh-11's.
31 Each line attached to the DH-11 communications multiplexer behaves as
33 described in tty(4). Input and output for each line may independently
34 be set to run at any of 16 speeds; see tty(4) for the encoding.
35 Bit 0200 of the minor device number for DH lines may be set to say that
37 a line is not properly connected, and that the line should be treated
38 as hard-wired with carrier always present. Thus creating the special
39 character device node "3, 130" via mknod /dev/ttyh2 c 3 130 would cause
40 line ttyh2 to be treated in this way. Bit 0100 of the minor device
41 number enables RTS/CTS (also called ``hardware'') flow control. It is
42 enabled by adding 64 to the minor device number: mknod /dev/ttyh2 c 3
43 194
44 The dh driver monitors the rate of input on each board, and switches
46 between the use of character-at-a-time interrupts and input silos.
47 While the silo is enabled during periods of high-speed input, the
48 driver polls for input 30 times per second.
49
51 /dev/tty[h-k][0-9a-f]
52 /dev/ttyd[0-9a-f]
53 /dev/MAKEDEV script to create special files
54 /dev/MAKEDEV.local script to localize special files
55
57 tty(4), dtab(5), autoconfig(8)
58
60 dh%d NXM. No response from UNIBUS on a dma transfer within a timeout
61 period. This has never been observed on a PDP-11 and is a carryover
62 from the VAX driver when it was ported. It is not serious.
63 dh%d %d overruns. The character input silo overflowed before it could
65 be serviced. This message is only printed at line close time. It is
66 not serious but does indicate that the system was not able to keep up
67 with the data flow.
683rd Berkeley Distribution May 31, 1997 DH(4)