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dhv(4) [bsd man page]

DHV(4)							     Kernel Interfaces Manual							    DHV(4)

NAME
dhv - DHV-11 communications multiplexer SYNOPSIS
/sys/conf/SYSTEM: NDHV dhv_units # DHV11 /etc/dtab: #Name Unit# Addr Vector Br Handler(s) # Comments dhv ? 160440 310 5 dhvrint dhvxint # dhv terminal mux major device number(s): raw: 24 minor device encoding: bits 0007 specify line on DHV unit bits 0070 specify DHV unit bit 0100 specifies RTS/CTS (``hardware'') flowcontrol bit 0200 specifies non-blocking open (``CD always on'') DESCRIPTION
A DHV-11 provides 8 communication lines. Each line attached to the DHV-11 communications multiplexer behaves as described in tty(4). Input and output for each line may indepen- dently be set to run at any of 13 speeds (50 and 200 baud are not available). While 38400 is available the underlying hardware is not fast enough to handle it and there will be pauses/gaps between characters. Bit 0200 of the minor device number for DHV lines may be set to say that a line is not properly connected, and that the line should be treated as hard-wired with carrier always present. Thus creating the special character device node "4, 130" via mknod /dev/ttyS2 c 4 130 would cause line ttyS2 to be treated in this way. Turning on bit 6 in the minor device number via mknod /dev/ttyS2 c 4 194 would enable RTS/CTS flow control. The DHV-11 has an input silo but does not have the programmable receiver delay that the DHU (and DHQ) have. Thus system services more interrupts (i.e. gets fewer characters per interrupt on average) with a DHV-11 than with a DHQ (in DHU mode). FILES
/dev/tty[S-Z][0-9a-f] SEE ALSO
tty(4) DIAGNOSTICS
dhv%d,%d NXM. No response from QBUS on a DMA transfer within a timeout period. This error has never been observed on a PDP-11 and is a carryover from the VAX driver when that was ported to 2BSD. dhv%d diag %o. Diagnostic information from the DHV11. This has never been observed. The DHV-11 hardware manual will be required to decode the value printed out. dhv%d: %d overruns. The character input silo overflowed before it could be serviced. This message is printed only when the line is closed. By only printing this when the line is closed further silo overruns are avoided (kernel printf statements are not interrupt driven). NOTES
The DHV lacks the receiver delay that the DHU (and DHQ) have. Thus it is extremely easy (indeed it's almost certain at higher data rates) for a DHV-11 to enter an interrupt per character mode and use 70-80% of the cpu. 3rd Berkeley Distribution May 31, 1997 DHV(4)

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DH(4)							     Kernel Interfaces Manual							     DH(4)

NAME
dh - DH-11/DM-11 communications multiplexer SYNOPSIS
/sys/conf/SYSTEM: NDH dh_units # DH11; NDH is in units of boards (16 each) NDM dm_units # DM11; NDM is in units of boards (16 each) /etc/dtab: #Name Unit# Addr Vector Br Handler(s) # Comments dm ? 170500 310 4 dmintr # dm11 dh modem control dh ? 160020 320 5 dhrint dhxint # dh11 terminal mux major device number(s): raw: 3 minor device encoding: bits 0017 specify line on DH unit bits 0060 specify DH unit bit 0100 specify RTS/CTS (``hardware'') flowcontrol bit 0200 specifies non-blocking open (``CD always on'') DESCRIPTION
A dh-11 provides 16 communication lines; dm-11's may be optionally paired with dh-11's to provide modem control for the lines. If there are fewer dm-11's than dh-11's, the dm-11's are assumed to be paired with the first dm_units dh-11's. Each line attached to the DH-11 communications multiplexer behaves as described in tty(4). Input and output for each line may indepen- dently be set to run at any of 16 speeds; see tty(4) for the encoding. Bit 0200 of the minor device number for DH lines may be set to say that a line is not properly connected, and that the line should be treated as hard-wired with carrier always present. Thus creating the special character device node "3, 130" via mknod /dev/ttyh2 c 3 130 would cause line ttyh2 to be treated in this way. Bit 0100 of the minor device number enables RTS/CTS (also called ``hardware'') flow con- trol. It is enabled by adding 64 to the minor device number: mknod /dev/ttyh2 c 3 194 The dh driver monitors the rate of input on each board, and switches between the use of character-at-a-time interrupts and input silos. While the silo is enabled during periods of high-speed input, the driver polls for input 30 times per second. FILES
/dev/tty[h-k][0-9a-f] /dev/ttyd[0-9a-f] /dev/MAKEDEV script to create special files /dev/MAKEDEV.local script to localize special files SEE ALSO
tty(4), dtab(5), autoconfig(8) DIAGNOSTICS
dh%d NXM. No response from UNIBUS on a dma transfer within a timeout period. This has never been observed on a PDP-11 and is a carryover from the VAX driver when it was ported. It is not serious. dh%d %d overruns. The character input silo overflowed before it could be serviced. This message is only printed at line close time. It is not serious but does indicate that the system was not able to keep up with the data flow. 3rd Berkeley Distribution May 31, 1997 DH(4)
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