MD2241-D128-V3 M-Systems Inc., MD2241-D128-V3 Datasheet - Page 29

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

8.3
8.3.1 PC Architectures
In current PC architectures, the first CPU fetch (after reset is negated) is mapped to the boot device area, also known
as the reset vector. The reset vector in PC architectures is located at address FFFF0, by using a Jump command to
the beginning of the BIOS chip (usually F0000 or E0000). The CPU executes the BIOS code, initializes the
hardware and loads DiskOnChip DIMM Plus software using the BIOS expansion search routine (e.g. D0000). Refer
to section 8.2 for a detailed explanation on the boot sequence in PC compatible platforms.
DiskOnChip DIMM Plus implements both disk and boot functions when it replaces the BIOS chip. To enable this,
DiskOnChip DIMM Plus requires a location at two different addresses:
This means that the CS# signal must be remapped between two different addresses. For further information on how
to achieve this, refer to application note AP-DOC-047 Designing DiskOnChip as a Flash Disk & Boot Device
Replacement.
8.3.2 Non-PC Architectures
In non-PC architectures, the boot code is executed from a boot ROM, and the drivers are usually loaded from the
storage device.
When using DiskOnChip DIMM Plus as the system boot device, the CPU fetches the first instructions from the
DiskOnChip DIMM Plus Programmable Boot Block, which contains the IPL. Since in most cases this block cannot
hold the entire boot loader, the Initial Program Loader (IPL) runs minimum initialization, after which the Secondary
Program Loader (SPL) is copied to RAM from flash. The remainder of the boot loader code then runs from RAM.
The IPL and SPL are located in a separate (binary) partition on DiskOnChip DIMM Plus, and can be hardware
protected if required.
For further information on software boot code implementation, refer to application note AP-DOC-070 Writing an
IPL for DiskOnChip Millennium Plus.
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Boot Replacement
If DiskOnChip DIMM Plus is used as the only disk in the system, the system boots directly from it and
assigns it drive C.
If DiskOnChip DIMM Plus is used with other disks in the system:
o
o
If DiskOnChip DIMM Plus is used as the OS boot device when configured as drive C, it must be formatted
as a bootable device by copying the OS files onto it. This is done by using the SYS command when running
DOS.
After power-up, DiskOnChip DIMM Plus must be mapped in F segment, so that the CPU fetches the reset
vector from address FFFF0, where DiskOnChip DIMM Plus is located.
After the BIOS code is loaded into RAM and starts execution, DiskOnChip DIMM Plus must be
reconfigured to be located in the BIOS expansion search area (e.g. D0000) so it can load the TrueFFS
software.
DiskOnChip DIMM Plus can be configured as the last drive (the default configuration). The system
assigns drive C to the hard disk and drive D to DiskOnChip DIMM Plus.
Alternatively, DiskOnChip DIMM Plus can be configured as the system’s first drive. The system
assigns drive D to the hard disk and drive C to DiskOnChip DIMM Plus.
Preliminary Data Sheet, Rev. 1.2
DiskOnChip DIMM Plus
94-SR-002-08-8L