Multiport serial cards install in a slot in a PC on the ISA or PCI bus. Instead of being called "... cards" they are also called "... adapters" or "... boards". Each such card provides you with many serial ports. Each card has a number of external connecters (DB-25 or RJ45 (telephone-like)) so that one may connect up a number of modems, etc. Each such modem is thus connected to its own serial port. Since the space on the external-facing part of the card is limited there is often not enough room for all the serial port connectors. To solve this problem, the connectors may be on the ends of cables which come out (externally) from the card. They may also be on little boxes which are connected by cable to the multiport card.
Dumb ones are not too much different than ordinary serial ports. They are interrupt driven and the CPU of the computer does most all the work servicing them. They usually have a system of sharing a single interrupt for all the ports. They usually require special drivers that you must put into the kernel or activate by modifying source code.
The serial ports your multiport board uses depends on what kind of board
you have. Some of these may be listed in detail in rc.serial
or in 0setserial
. These files may be in the
setserial
package. I highly recommend getting the latest
version of setserial
if you are trying to use multiport boards.
You will probably need to create these devices. Either use the
mknod
command, or the MAKEDEV
script. Devices (in the /dev
directory) for serial ports are made by adding ``64 + port number''.
So, if you wanted to create devices for ttyS17
, you would
type:
linux# mknod -m 666 /dev/cua17 c 5 81
linux# mknod -m 666 /dev/ttyS17 c 4 81
Note that ``64 + 17 = 81''. Using the MAKEDEV
script, you would
type:
linux# cd /dev
linux# ./MAKEDEV ttyS17
Besides the listing of various brands of multiports found in this HOWTO there is Gary's Encyclopedia - Serial Cards. It's not as complete, but may have some different links.
Standard PC serial boards (COM1 - COM4) can be used to, to connect external serial devices (modems, serial mice, etc...). Since PC's no longer come with them (but have the chips for this purpose mounted on the motherboard), they are hard to find in retail stores. An internal modem for the ISA bus may include a built-in serial port.
Note: due to address conflicts, you may not be able to use COM4 and IBM8514 video board (or clones) simultaneously. See Avoiding IO Address Conflicts with Certain Video Boards
They are also called "serial adapters".
* => The file that ran setserial in Debian shows some details of configuring
# => See note below for this board
In general, Linux will support any serial board which uses a 8250, 16450, 16550, 16550A, 16650, etc. UART. See the latest man page for "setserial" for a more complete list.
Notes:
AST Fourport: You might need to specify skip_test
in rc.serial
.
BB-1004 and BB-1008 do not support DCD and RI lines, and thus are not usable for dialin modems. They will work fine for all other purposes.
Digi PC/8 Interrupt Status Register is at 0x140.
SIIG IO1812 manual for the listing for COM5-COM8 is wrong. They should be COM5=0x250, COM6=0x258, COM7=0x260, and COM8=0x268.
Make sure that a Linux-compatible driver is available and read the information that comes with it. These boards use special devices (in the /dev directory), and not the standard ones. This information varies depending on your hardware. If you have updated info please send it to me.
info@comtrol.com
or
http://www.comtrol.com
ftp://tsx-11.mit.edu/pub/linux/packages/comtrol
sales@cyclades.com
or
http://www.cyclades.com
ftp://ftp.cyclades.com/pub/cyclades
and included in Linux
kernel since version 1.1.75
pccom8@signum.se
ftp://ftp.signum.se/pub/pccom8
sales@dgii.com
or
http://www.dgii.com
ftp://ftp.dgii.com/drivers/linux
and
included in Linux kernel since version 2.0
si@wimpol.demon.co.uk
sales@equinox.com
or
http://www.equinox.com
ftp://ftp.equinox.com/library/sst
spot@gtek.com
or
http://www.gtek.com
ftp://ftp.gtek.com/pub
arobinso@nyx.net
or
http://www.nyx.net/~arobinso
http://www.nyx.net/~arobinso
and included in Linux
kernel since version 2.1.15. Setserial 2.15+ supports.
info@maxpeed.com
or
http://www.maxpeed.com
ftp://maxpeed.com/pub/ss
info@moxa.com.tw
or
http://www.moxa.com.tw
ftp://ftp.moxa.com.tw/drivers/c218-320/linux
sales@sdlcomm.com
or
http://www.sdlcomm.com
ftp://ftp.sdlcomm.com/pub/drivers
sales@stallion.com
or
http://www.stallion.com
ftp://ftp.stallion.com/drivers/ata5/Linux
and
included in linux kernel since 1.3.27
A review of Comtrol, Cyclades, Digi, and Stallion products was printed
in the June 1995 issue of the Linux Journal. The article is
available at
http://www.ssc.com/lj/issue14
.