ast —
multiplexing serial communications interface
ast0 at isa? port 0x1a0 irq 5
com2 at ast? slave ?
com3 at ast? slave ?
com4 at ast? slave ?
com5 at ast? slave ?
The ast driver provides support for boards that
multiplex together up to four EIA RS-232C (CCITT V.28) communications
interfaces. Apparently the original maker of hardware using this multiplexing
protocol was AST.
Each ast device is the master device for
up to four com devices. The kernel configuration
specifies these com devices as slave devices of the
ast device, as shown in the synopsis. The slave ID
given for each com device determines which bit in
the interrupt multiplexing register is tested to find interrupts for that
device. The port specification for the ast device is
used to compute the base addresses for the com
subdevices and the port for the interrupt multiplexing register.
The ast driver was written by Roland McGrath and placed
into the public domain.