AST(4) | Device Drivers Manual | AST(4)

# NAME

`ast` —
multiplexing serial communications interface

# SYNOPSIS

`ast0 at isa? port 0x1a0 irq 5`
`com2 at ast? slave ?`
`com3 at ast? slave ?`
`com4 at ast? slave ?`
`com5 at ast? slave ?`

# DESCRIPTION

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.

# FILES

/dev/tty0?

# SEE ALSO

com(4)

# HISTORY

The `ast` driver was written by Roland McGrath and placed into the public domain.

March 30, 1994 | NetBSD 10.0