.\"
.\" SPDX-License-Identifier: BSD-2-Clause
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.\" Copyright (c) 2010 Lev Serebryakov <lev@FreeBSD.org>.
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.\" This code is derived from software contributed to The NetBSD Foundation
.\" by Lennart Augustsson.
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.Dd September 21, 2026
.Dt UMCS 4
.Os
.Sh NAME
.Nm umcs
.Nd ASIX/MosChip MCS7840/MCS7820 USB to serial UART driver
.Sh SYNOPSIS
.Cd device usb
.Cd device ucom
.Cd device umcs
.Pp
In
.Xr loader.conf 5 :
.Cd umcs_load="YES"
.Sh DESCRIPTION
The
.Nm
driver provides support for various multiport serial adapters
based on the ASIX/MosChip MCS7840 and MCS7820 chips.
They are 2- or 4-port adapters with full-featured
16550-compatible UARTs and very flexible baud generators.
Also, these chips
support RS422/RS485 and IrDA operations.
.Pp
The device is accessed through the
.Xr ucom 4
driver which makes it behave like a
.Xr tty 4 .
.Pp
Different ports on device are presented as sub-units, like
.Pa /dev/ttyU0.1
and
.Pa /dev/ttyU0.2 .
.Sh HARDWARE
The
.Nm
driver supports the following USB to serial UART controllers
based on the ASIX/MosChip MCS7840 and MCS7820:
.Pp
.Bl -bullet -compact
.It
ST Lab U-360 two-port serial USB adapter
.It
ST Lab U-400 four-port serial USB adapter
.El
.Sh FILES
.Bl -tag -width "/dev/ttyU*.*.init" -compact
.It Pa /dev/ttyU*.*
for callin ports
.It Pa /dev/ttyU*.*.init
.It Pa /dev/ttyU*.*.lock
corresponding callin initial-state and lock-state devices
.Pp
.It Pa /dev/cuaU*.*
for callout ports
.It Pa /dev/cuaU*.*.init
.It Pa /dev/cuaU*.*.lock
corresponding callout initial-state and lock-state devices
.El
.Sh SEE ALSO
.Xr tty 4 ,
.Xr ucom 4 ,
.Xr usb 4
.Sh HISTORY
The
.Nm
driver
appeared in ports since December of 2010.
.Sh AUTHORS
.An -nosplit
The
.Nm
driver was written by
.An Lev Serebryakov Aq Mt lev@FreeBSD.org .
.Sh BUGS
This driver doesn't support access to any fine tunes of
chip, like RS522/RS485 mode, non-standard baudrates, etc.