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)
Check Out this Related Man Page
ace(7) Miscellaneous Information Manual ace(7)NAME
ace - Serial communications interface
SYNOPSIS
controller ace0 at * slot ? vector aceintr
DESCRIPTION
The ace serial line controller provides a serial communications interface on DEC 2000, AlphaStation, and AlphaServer platforms. The serial
communications ports that are controlled by ace adhere to the RS-232 standard and can operate at rates from 50 to 115200 baud (see tty(7)).
These communications ports support serial-line printers, modems, and terminals.
In alternate console configurations (that is, no graphics head), the terminal to be the system console must be connected to the port that
is mapped to /dev/tty00. (See ports(7) for information about mapping AlphaStation and AlphaServer port labels to device pathnames.) Cur-
rently, some processors that use the ace driver limit the serial console port to 9600 baud, 8-bit, no parity and no modem support. However,
some processor consoles do support baud rates other than 9600 baud and allow the use of modems as console devices. Consult your hardware
documentation to determine the type of console support your system provides.
The driver for the ace interface supports hardware flow control using the Request to Send (RTS) and Clear to Send (CTS) signals. When
hardware flow control is enabled, the flow of input data is controlled by the RTS signal and the flow of output data is controlled by the
CTS signal. If the CTS signal is off, the driver suspends output to that line until the CTS lead is reasserted. Likewise the driver turns
off the RTS lead to tell the device connected to the line to stop sending data as a result of congestion on the host side. When the condi-
tion clears, the driver turns on the RTS lead to tell the device to resume sending data.
The DCD (carrier detect) timer value defaults to 2 seconds. This value may be changed if your modem hardware requires a different value.
the change can be made in the /etc/sysconfigtab file as follows:
ace: dcd_timer=n
where n is the time interval in seconds, and can be set to 0 (no timeout), 1, or 2 seconds. Alternatively, you can use the sysconfig com-
mand to set the same time interval option as follows:
# sysconfig -r ace dcd_timer=[n]
If you use the sysconfig command, the value will not be preserved when the system is rebooted. To preserve the setting, put the entry in
the /etc/sysconfigtab file
NOTES
If you are using the alternate system console to perform kernel debugging, you must change the kdebug entry in the /etc/remote file to use
/dev/tty01; when the kernel is running in debugging mode, no other application can use the port. See Kernel Debugging for information on
setting up your system for kernel debugging.
RESTRICTIONS
Unless alternative specifications are stated in your system hardware documentation, data communications equipment attached to the console
serial port in alternate console configurations must be set to 9600 baud, 8-bits, no parity. If a serial console is being used, /dev/tty00
cannot be opened by another process. The ace driver enforces this restriction.
Baud rates greater than 38400 are not supported on the two primary serial ports on the DEC 2000 system. However, if you use an ISA serial
or modem card that is capable of communicating at the higher rates, the higher rates are supported.
FILES
console terminal local terminal local terminal
RELATED INFORMATION MAKEDEV(8), console(7), devio(7), modem(7), ports(7), tty(7)
Kernel Debugging
System Administration delim off
ace(7)