MD2241-D128-V3 M-Systems Inc., MD2241-D128-V3 Datasheet - Page 28

• Manufacturer Part Number: MD2241-D128-V3
• Description: Diskonchip Dimm Plus
• Manufacturer: M-Systems Inc.

8.
8.1
DiskOnChip DIMM Plus can function both as a flash disk and the system boot device.
If DiskOnChip is configured as a flash disk, it can operate as the OS boot device. DiskOnChip default firmware
contains drivers to enable it to perform as the OS boot device under DOS (see section 8.2). For other OSs, please
refer to the readme file of the TrueFFS driver.
If DiskOnChip DIMM Plus is configured as a flash disk and as the system boot device, it contains the boot loader,
an OS image and a file system. In such a configuration, DiskOnChip DIMM Plus can serve as the only non-volatile
device on board. Refer to section 8.3.2 for further information on boot replacement.
8.2
When used in PC compatible platforms, DiskOnChip DIMM Plus is connected to an 8KB memory window in the
BIOS expansion memory range, typically located between 0C8000H to 0EFFFFH. During the boot process, the
BIOS loads the TrueFFS firmware into the PC memory and installs DiskOnChip as a disk drive in the system. When
the operating system is loaded, DiskOnChip is recognized as a standard disk. No external software is required to
boot from DiskOnChip.
Figure 12 illustrates the location of the DiskOnChip DIMM Plus memory window in the PC memory map.
After reset, the BIOS code first executes the Power On Self-Test (POST) and then searches for all expansion ROM
devices. When DiskOnChip DIMM Plus is found, the BIOS code executes from it the IPL (Initial Program Loader)
code, located in the XIP portion of the Programmable Boot Block. This code loads the TrueFFS driver into system
memory, installs DiskOnChip DIMM Plus as a disk in the system, and then returns control to the BIOS code. The
operating system subsequently identifies DiskOnChip DIMM Plus as an available disk. TrueFFS responds by
emulating a hard disk.
From this point onward, DiskOnChip DIMM Plus appears as a standard disk drive. It is assigned a drive letter and
can be used by any application, without any modifications to either the BIOS set-up or the autoexec.bat/
config.sys files. DiskOnChip DIMM Plus can be used as the only disk in the system, with or without a floppy drive,
and with or without hard disks. The drive letter assigned depends on how DiskOnChip DIMM Plus is used in the
system, as follows:
28
Booting from DiskOnChip DIMM Plus
Introduction
Boot Procedure in PC Compatible Platforms
Figure 12: DiskOnChip DIMM Plus Memory Window in PC Memory Map
Preliminary Data Sheet, Rev. 1.2
0FFFFFH
0C8000H
0B0000H
0F0000H
Extended Memory
DiskOnChip
Display
BIOS
RAM
1M
640k
0
8k
DiskOnChip DIMM Plus
94-SR-002-08-8L