The Specialix SI/XIO and SX hardware makes up an 8 to 32 port RS-232 serial multiplexor.
The system uses two components: a "Host adapter", which is plugged into an ISA, EISA or PCI slot and provides intelligence and buffering/processing capabilities, as well as an external bus in the form of a 37 pin cable.
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 outside 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 Irqs 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 configuring 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
.Fx ) 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.