Chapter 1 – Introduction
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An on-board switch controls which part of the Flash device is loaded into shadow
DRAM. This allows you to update half the Flash device and still retain a copy of the
original BIOS if the update is not successful or the BIOS is incorrect. To determine
which section of the BIOS is being used, write to port 219h (bit 2=0) and then read bit 3
from port 219h. If bit 3 returns a zero, the lower portion of the BIOS is being used.
Serial and Parallel Ports
PC/AT peripherals include two high-speed 16550-compatible serial ports, one ECP/EPP
parallel port, and a PS/2-compatible keyboard port.
Keyboard Interface
The keyboard interface uses a PS/2-style connector out the front panel. The +5 V is
protected with a polyswitch. This device opens if the +5 V is shorted to GND. Once the
shorting condition is removed, the polyswitch will allow current flow to resume.
Hard and Floppy Drives
The XVME-655’s IDE hard drive and floppy drive signals are routed through the P2
connector, providing a simplified method of connecting external floppy and hard drives.
The XVME-655 supports only one floppy drive.
When used with the XVME-977 mass storage module, hard and floppy drives do not
have to be located next to the processor. The XVME-977 can be installed in any
unoccupied VMEbus slot, and then connected to the XVME-655 through a cable on the
J2 connectors. This allows greater flexibility in configuring a VMEbus card cage.
For applications that require mass storage outside the VMEbus chassis, the XVME-973
driver adapter module plugs onto the VMEbus P2 connector. This module provides
industry standard connections for IDE and floppy signals. You can connect one floppy
drive to the XVME-973. This drive may be 2.88 Mbytes, 1.44 Mbytes, 1.2 Mbytes, 720
Kbytes, or 360 Kbytes.
Caution
The total cable length must not exceed 18 inches. Also, if two drives are
connected, they must be no more than six inches apart.
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