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PCWEASEL(4) NetBSD Kernel Interfaces Manual PCWEASEL(4)
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pcweasel -- Support for the PC-Weasel serial console board
weasel* at pci? dev ? function ?
Note that the appropriate display device must also be enabled. See
pcdisplay(4) for more information.
The PC-Weasel is a serial console board for use primarily on Intel-based
PC-class systems. It addresses a problem that nearly everyone who has
deployed a PC-class server has experienced: the total lack of remote man-
agement capability on PC-class hardware.
In addition to serial console support, the PC-Weasel provides the ability
to remotely reset the system (by means of a hardware reset signal), and
provides a watchdog timer function.
The PC-Weasel works by emulating the original IBM Monochrome Display
Adapter (MDA). Writes to the display's character cells are translated
into ANSI terminal sequences which are then sent out the PC-Weasel's
serial port. Incoming characters are translated into PC keyboard scan
codes and then fed (by means of a cable) into the system's keyboard con-
troller. The system believes it is using a display console. This is
particularly important in the event that one needs access to BIOS config-
The PC-Weasel also includes a ST16550 serial port, which may be config-
ured as any one of the system's serial ports. Typical usage is to con-
figure the port as com0 at ISA I/O address 0x3f8. When the PC-Weasel
detects activity on the ST16550, the serial port is automatically con-
nected to the ST16550 so that the serial port may be used as normal.
When the PC-Weasel detects activity on the internal UART used for MDA
emulation, the serial port is automatically reconnected to the emulation
UART. This allows the boot program and kernel to be configured to use
the serial port directly (which is more efficient than using the MDA emu-
lation mode), yet allows the MDA emulation to be reestablished as soon as
the kernel loses control of the system.
The pcweasel driver provides support for the additional features present
on the PC-Weasel. At the moment, this includes support for the watchdog
timer function. Use of the pcweasel driver is not required in order for
the system to function with a PC-Weasel installed so long as only the MDA
emulation and ST16550 serial port functionality is required.
The pcweasel driver first appeared in NetBSD 1.5.1.
The PC-Weasel was invented by Herb Peyerl and Jonathan Levine at Canada
The pcweasel driver was written by Jason R. Thorpe <email@example.com>,
and contributed by Zembu Labs, Inc. Herb Peyerl of Middle Digital, Inc.
provided several firmware updates during the development of the driver.
NetBSD 9.99 November 23, 2007 NetBSD 9.99