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Motherboard Description
15
1.8 PC87307 Super I/O Controller
Control for the integrated serial ports, parallel port, floppy drive, real-time clock, and keyboard
controller is incorporated into a single component, the National Semiconductor PC87307. The
PC87307 is a fully Plug and Play compatible device which provides:
• Two NS16C550-compatible UARTs with send/receive 16 byte FIFO
Support for an IrDA and Consumer IR compliant Infrared interface
• Multi-mode bi-directional parallel port
Standard mode; IBM
†
and Centronics
†
compatible
Enhanced Parallel Port (EPP) with BIOS/Driver support
High Speed mode; Extended Capabilities Port (ECP) compatible
• Industry standard floppy controller with 16 byte data FIFO (2.88 MB floppy support)
• Integrated Real Time Clock with Century calendar functionality
• Integrated 8042 compatible keyboard controller
The PC87307 is normally configured automatically by the BIOS, but configuration of these
interfaces also is possible using the CMOS Setup utility that can be invoked during boot. The
serial ports can be enabled as COM1, COM2, COM2 as IrDA, or disabled. The parallel port can
be configured as compatible, bi-directional, EPP/ECP, or disabled. The floppy interface can be
configured for 360 KB or 1.2 MB 5¼" media or for 720 KB, 1.2 MB, 1.44 MB, or 2.88 MB
3½" media.
1.8.1 Floppy Controller
The PC87307 is software compatible with the DP8473 and 82077 floppy disk controllers. The
floppy interface can be configured for 360 KB or 1.2 MB 5¼" media or for 720 KB, 1.2 MB,
1.44 MB, or 2.88 MB 3½" media in the BIOS setup. By default, the Floppy A interface is
configured for 1.44 MB and Floppy B is disabled. Configuring the floppy interface for 1.2 MB
3½" (3-mode floppy) requires the use of a driver to operate correctly.
1.8.2 Keyboard and Mouse Interface
PS/2 keyboard/mouse connectors are located on the back panel side of the motherboard. The 5V
lines to these connectors are protected with a PolySwitch
†
circuit which acts much like a self-
healing fuse, re-establishing the connection after an over-current condition is removed. While this
device eliminates the possibility of having to replace a fuse, care should be taken to turn off the
power before installing or removing a keyboard or mouse.
The integrated 8042 microcontroller contains the AMI Megakey keyboard/mouse controller code
which, besides providing traditional keyboard and mouse control functions, supports Power-
On/Reset (POR) password protection. The POR password can be defined by the user in the Setup
program. The keyboard controller also provides for the following “hot-key” sequences:
• <CTRL> <ALT> <DEL>: System software reset. This sequence performs a software reset of
the computer by jumping to the beginning of the BIOS code and running the POST operation.