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RTFPS(4)                 BSD Kernel Interfaces Manual                 RTFPS(4)

NAME
     rtfps -- multiplexing serial communications interface

SYNOPSIS
     rtfps0 at isa? port 0x1230 irq 10
     com* at rtfps?

DESCRIPTION
     The rtfps driver provides support for IBM RT PC boards that multiplex
     together up to four EIA RS-232C (CCITT V.28) or RS-422A communications
     interfaces.

     Each rtfps device is the master device for up to four com devices.  The
     kernel configuration specifies these com devices as slave devices of the
     rtfps device, as shown in SYNOPSIS.  The port specification for the rtfps
     device is used to compute the base addresses for the com subdevices.

FILES
     /dev/tty0?

SEE ALSO
     com(4), intro(4), isa(4)

HISTORY
     The rtfps driver was written by Charles Hannum, based on the ast driver.

BUGS
     The rtfps driver is unlikely to work on non-EISA and non-PCI machines.
     The ISA bus only asserts 10 I/O address lines, and this is not enough.

     Even on EISA and PCI machines, some address conflicts have been observed.
     On one machine, the second port always conflicted with something (though
     it's not clear what) and caused strange results.  Disabling the second
     port in the kernel config allowed the other three ports to function cor-
     rectly.

BSD                              May 30, 2017                              BSD