asyc(7)


asyc -- asynchronous serial ports driver

Description

The asyc driver supports both the system board serial port and an additional serial adapter simultaneously. While up to four serial ports are supported, the system default enables two serial ports. If an adapter for a port is not installed, an attempt to open it will fail. Depending on your system processor type and UART, the port can be programmed for a range of speeds from 50 to 115200 baud, character length, and parity. Output speed is always the same as input speed. The port behaves as described in termio(7)

The asynchronous port is a character-at-a-time device for both input and output. This characteristic both limits the bandwidth that can be achieved over a serial line, and increases the interrupt loading on the central processor. Applications like uucp(1bnu) and PPP may be able to function well at speeds greater than 9600 baud, depending on your system processor type and UART.

The serial port adapter's programmable baud rates do not correspond exactly with system baud rates. Specifically, setting B0 will cause a disconnect, setting EXTA will set 19200 baud, and setting EXTB will set 38400 baud. The asynchronous ports driver supports interrupt sharing, as well as line signal (hardware) flow control when the device node /dev/tty0?h is used. The /dev/tty0?s ports are software flow control nodes as are the /dev/tty0? nodes.

The asyc driver supports both 16450 and 16550 UARTs and equivalents.

Files

/dev/tty*

/dev/term/*

Usage

To activate additional ports use the /sbin/dcu command; see dcu(1M). Apply the changes and exit dcu.


NOTE: You need to reboot the system for the additional ports to work.

The order of entries in the DCU and the corresponding entries in the asyc driver's space.c file must be in the same order for serial consoles to work correctly.


Diagnostics

When using dcu to activate additional ports that share interrupts, if you notice a message like IRQ conflicts with an interrupt vector which cannot be shared..., you need to change the ``ITYPE'' field to 3; apply the change, exit dcu and reboot the system.

References

dcu(1M), termio(7), termiox(7)
30 January 1998
© 1998 The Santa Cruz Operation, Inc. All rights reserved.