SI(4) BSD Kernel Interfaces Manual SI(4)NAMEsi — driver for Specialix International SI/XIO or SX intelligent serial
For ISA host cards put the following lines in /boot/device.hints:
The Specialix SI/XIO and SX hardware makes up an 8 to 32 port RS-232
The system uses two components: a "Host adapter", which is plugged into
an ISA, EISA or PCI slot and provides intelligence and buffering/process‐
ing capabilities, as well as an external bus in the form of a 37 pin
On this cable, "modules" are connected. The "SI" module comes in a 4 and
8 port version. The "XIO" and "SX" modules come only in 8 port versions.
The host adapter polls and transfers data between the modules and the
rest of the machine. The Host adapter provides a 256 byte transmit and
256 byte receive FIFO for each of the 32 ports that it can maintain.
The XIO modules can operate each of their 8 ports at 115,200 baud. The
SI version can run at 57,600 baud. The SX modules can operate each of
their 8 ports at up to 921,600 baud.
SX modules are only supported when connected to an SX host card. SI or
XIO modules are supported on any host card.
The host adapter uses a shared memory block in the traditional ISA bus
"hole" between 0xA0000 and 0xEFFFF. The adapter can be configured out‐
side range, but requires the memory range to be explicitly non-cached.
The driver does not yet support this mode of operation.
SX ISA Host cards have an 8/16 bit mode switch or jumper on them. This
switch or jumper MUST be set for 8 bit mode.
The ISA adapters can use Irq's 11, 12 or 15 (and 9 and 10 in the case of
SX host cards).
The si device driver may have some of its configuration settings changed
at run-time with the sicontrol(8) utility.
The si device driver also responds to the comcontrol(8) utility for con‐
figuring drain-on-close timeouts.
The driver also defines 3 sysctl variables that can be manipulated:
machdep.si_debug sets the debug level for the whole driver. It depends
on the driver being compiled with SI_DEBUG. machdep.si_pollrate sets how
often per second the driver polls for lost interrupts.
machdep.si_realpoll sets whether or not the card will treat the poll
intervals as if they were interrupts.
An open on a /dev device node controlled by the si driver obeys the same
semantics as the sio(4) driver. It fully supports the usual semantics of
the cua ports, and the "initial termios" and "locked termios" settings.
In summary, an open on a tty port will block until DCD is raised, unless
O_NONBLOCK is specified. CLOCAL is honored. An open on a cua port will
always succeed, but DCD transitions will be honored after DCD rises for
the first time.
Up to four SI/XIO host cards may be controlled by the si driver. Due to
the lack of available interrupts, only 3 ISA SI/XIO host cards can be
used at once.
The lowest 5 bits of the minor device number are used to select the port
number on the module cluster. The next 2 bits select which of 4 host
adapter cards. This allows a maximum of 128 ports on this driver.
Bit 7 is used to differentiate a tty/dialin port (bit 7=0) and a
cua/callout port (bit 7=1).
Bit 8 through 15 (on FreeBSD) are unavailable as they are a shadow of the
major device number.
If bit 16 is a 1, the device node is referring to the "initial state"
device. This "initial state" is used to prime the termios(4) settings of
the device when it is initially opened. If bit 17 is a 1, the device
node is referring to the "locked state" device. The "locked state" is
used to prevent the termios(4) settings from being changed.
To manipulate the initial/locked settings, the stty(1) command is useful.
When setting the "locked" variables, enabling the mode on the lock device
will lock the termios mode, while disabling the mode will unlock it.
/dev/si_control global driver control file for sicontrol(8)
/dev/ttyA* terminal/dialin ports
/dev/cuaA* dialout ports
/dev/ttyiA* initial termios state devices
/dev/ttylA* locked termios state devices
/dev/cuaiA* initial termios state devices for dialout ports
/dev/cualA* locked termios state devices for dialout ports
SEE ALSOstty(1), sio(4), termios(4), tty(4), comcontrol(8), sicontrol(8)HISTORY
This driver is loosely based on driver code originating at Specialix,
which was ported to run on BSDI by Andy Rutter ⟨email@example.com⟩.
The System V driver source is/was available by ftp from
This driver is not supported by Specialix International.
Peter Wemm ⟨firstname.lastname@example.org⟩ obtained the code from Andy Rutter and
ported it to FreeBSD and threw the man page together. Bruce Evans
⟨email@example.com⟩ provided a large amount of assistance during porting.
Nick Sayer ⟨firstname.lastname@example.org⟩ wrote the EISA, PCI and SX portions.
The interrupt tuning rate is not believed to be optimal at this time for
Polled mode (a feature of standard Specialix drivers) is not implemented,
but it can be approximated by turning on machdep.si_realpoll. The poll
frequency is set by machdep.si_pollrate (in units of 1/100th of a sec‐
The driver does not yet support baud rates higher than 115,200 on SX mod‐
Operation outside the traditional ISA "hole" is not yet supported,
although it should work if the test is removed from the probe routine.
Multiple host cards are supported although combinations of hosts on dif‐
ferent bus types have not been tested - device numbering is known to be a
problem and may lead to unexpected results.
BSD September 16, 1995 BSD