---
name: "hsq"
section: "4"
platform: "openbsd"
package: "man"
version: "8.0-current-20261101"
release: "OpenBSD 8.0-current (2026-11-01)"
platforms: ["openbsd"]
url: "https://new.carta.tech/hsq"
---

# hsq(4)

multiplexing serial communications interface

## NAME

**hsq** – multiplexing serial communications interface

## SYNOPSIS

**hsq0 at isa? port 0x140 irq 10** **com\* at hsq?**

## DESCRIPTION

The **hsq** driver provides support for Hostess (*Comtrol Corporation:* **https://www.comtrol.com/**) and compatible boards that multiplex together up to four EIA RS-232C (CCITT V.28) communications interfaces.

Each **hsq** device is the master device for up to four **com** devices. The kernel configuration specifies these **com** devices as slave devices of the **hsq** device, as shown in 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 **hsq** device is used to compute the base addresses for the **com** subdevices (they are equal to port + ID \* 8) and the port for the interrupt multiplexing register (it is equal to port + 7). More technical details on how the driver works can be found in the big comment at the beginning of the driver's source code.

Information on setup of card's configuration switches should be taken from Comtrol Corporation's web site, since the author wrote and tested the driver only with Hostess-compatible cards.

## FILES

- */dev/tty0?*

  - */dev/cua0?*

  ## SEE ALSO

[com(4)](/com/4.md), [intro(4)](/intro/4.md), [isa(4)](/isa/4.md)

## HISTORY

The **hsq** driver was written by Denis A. Doroshenko based on the [ast(4)](/ast/4.md) driver.