---
name: "umcs"
section: "4freebsd"
platform: "linux"
package: "freebsd-manpages"
version: "12.2-2"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/umcs/4freebsd"
---

# umcs(4freebsd)

USB support for serial adapters based on the MCS7820 and MCS7840 chips

## NAME

**umcs** – USB support for serial adapters based on the MCS7820 and MCS7840 chips

## SYNOPSIS

To compile this driver into the kernel, place the following lines in your kernel configuration file:

**device usb** **device ucom** **device umcs**

Alternatively, to load the driver as a module at boot time, place the following line in [loader.conf(5)](/loader.conf/5.md):

```
umcs_load="YES"
```

## DESCRIPTION

The **umcs** driver provides support for various multiport serial adapters based on the MosCom MCS7820 and MCS7840 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.

The device is accessed through the [ucom(4)](/ucom/4.md) driver which makes it behave like a [tty(4)](/tty/4.md).

Different ports on device are presented as sub-units, like */dev/ttyU0.1* and */dev/ttyU0.2*.

## HARDWARE

The **umcs** driver was tested on the following adapters:

- ST Lab U-360 two-port serial USB adapter

- ST Lab U-400 four-port serial USB adapter

## FILES

- */dev/ttyU\*.\**

  for callin ports

- */dev/ttyU\*.\*.init*

  - */dev/ttyU\*.\*.lock*

  corresponding callin initial-state and lock-state devices

- */dev/cuaU\*.\**

  for callout ports

- */dev/cuaU\*.\*.init*

  - */dev/cuaU\*.\*.lock*

  corresponding callout initial-state and lock-state devices

## SEE ALSO

[tty(4)](/tty/4.md), [ucom(4)](/ucom/4.md), [usb(4)](/usb/4.md)

## HISTORY

The **umcs** driver appeared in ports since December of 2010.

## AUTHORS

The **umcs** driver was written by Lev Serebryakov ⟨*lev@FreeBSD.org*⟩.

## BUGS

This driver doesn't support access to any fine tunes of chip, like RS522/RS485 mode, non-standard baudrates, etc.