ast - multiplexing serial communications interface
ast0 at isa? port 0x1a0 irq 5
ast1 at isa? port 0x2a0 irq 6
com* at ast? slave ?
pccom* at ast? slave ?
The ast driver provides support for boards that multiplex
together up to
four EIA RS-232C (CCITT V.28) communications interfaces.
original master of hardware using this multiplexing protocol
Each ast device is the master device for up to four com or
The kernel configuration specifies these com devices as
slave devices of
the ast device, as shown in SYNOPSIS. The slave ID given
for each com
device determines which bit in the interrupt multiplexing
tested to find interrupts for that device. The port specification for
the ast device is used to compute the base addresses for the
and the port for the interrupt multiplexing register.
On a real AST card, the jumpers are as follows:
SW1-1 Turn ON for irq 2. Default is OFF.
SW1-2 Turn ON for irq 3. Default is OFF.
SW1-3 Turn ON for irq 4. Default is OFF.
SW2-1 Turn ON for irq 5. This is ON for the first card,
SW2-2 Turn ON for irq 6. This is ON for the second card,
SW2-3 Turn ON for irq 7. Default is OFF.
SW3-1 ``Compatible mode''. The ast driver needs extended
mode, so leave
SW3-2 IO Address. In extended mode, this should be OFF for
card at 0x1a0-0x1a7 and ON for the second card at
SW3-3 Interrupt sharing. Default is OFF.
SW3-4 Reserved, must be OFF.
com(4), intro(4), isa(4)
The ast driver was written by Roland McGrath and placed into
OpenBSD 3.6 March 30, 1994
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