AST(4) | Device Drivers Manual | AST(4) |
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.
March 30, 1994 | NetBSD 10.99 |