multiplexing serial communications
addcom0 at isa? port 0x108 irq 5
com* at addcom?
driver provides support for Addonics
FlexPort 8/S (and probably FlexPort 4/S) boards that multiplex together up to
eight (or four) EIA RS-232C (CCITT V.28) communications interfaces.
device is the master device for up to
devices. The kernel configuration
specifies these com
devices as slave devices of
device, as shown in
. The slave ID given for
device determines which bit in the
interrupt multiplexing register is tested to find interrupts for that device.
The port specification for the addcom
used to compute the base addresses for the com
subdevices. The port for the interrupt multiplexing register is fixed, so it
is doubtful that more than one addcom
can be used
in a machine.
support for addcom
devices first appeared in OpenBSD 3.0