MD3331-D64-V3 M-Systems Inc., MD3331-D64-V3 Datasheet - Page 24

• Manufacturer Part Number: MD3331-D64-V3
• Description: Diskonchip Millennium Plus
• Manufacturer: M-Systems Inc.

3.5
During boot, code must be executed directly from the flash media, rather than first copied to the host RAM and then
executed from there. This direct XIP code execution capability is essential for booting.
The Programmable Boot Block with XIP capability enables DiskOnChip Millennium Plus to act as a boot ROM
device in addition to being a flash disk. This unique design enables the user to benefit from the advantages of NOR
flash, typically used for boot and code storage, and NAND flash, typically used for data storage. No other boot
device is required on the motherboard.
The Programmable Boot Block on DiskOnChip Millennium Plus 16/32MB consists of 1KB of programmable boot
block, and DiskOnChip 64MB provides a 2KB Programmable Boot Block. The Download Engine (DE) described in
the next section expands the functionality of this block by copying the boot code from the flash into the boot block.
When two, three or four DiskOnChip Millennium Plus devices are cascaded, the Programmable Boot Block is
respectively accumulated, providing 2, 3 or 4KB of boot block. The Programmable Boot Block of each device is
mapped to a unique address space.
Note: Up to two DiskOnChip Millennium Plus 64MB devices can be cascaded, providing a Programmable Boot
3.6
Upon power up or when the RSTIN# signal is asserted high, the DE automatically downloads the Initial Program
Loader from the flash to the Programmable Boot Block. The Initial Program Loader (IPL) is responsible for starting
the boot process. The download process is quick (1.3 ms max) and is designed so that when the CPU accesses
DiskOnChip for code execution, the IPL code is already located in the Programmable Boot Block.
In addition, the DE downloads the Data Protection Structures (DPS) from the flash to the Protection State Machines
(PSMs), so that DiskOnChip is secure and protected from the first moment it is active.
During the download process, DiskOnChip Millennium Plus asserts the BUSY# signal to indicate to the system that
it is not yet ready to be accessed. Once BUSY# is negated, the system can access the DiskOnChip Millennium Plus.
A failsafe mechanism prevents improper initialization due to a faulty VCC or invalid assertion of the RSTIN# input.
Another failsafe mechanism is designed to overcome possible NAND flash data errors. It prevents internal registers
from powering up in a state that bypasses the intended data protection. In addition, in any attempt to sabotage the
data structures causes the entire DiskOnChip Millennium Plus to become both read and write-protected and
completely inaccessible.
3.7
NAND flash, being an imperfect memory, requires error handling. DiskOnChip Millennium Plus implements
Reed-Solomon Error Detection Code (EDC). A hardware-generated, 6-byte error detection signature is computed
each time a page (512 bytes) is written to or read from DiskOnChip.
The TrueFFS driver implements complementary Error Correction Code (ECC). Unlike error detection, which is
required on every cycle, error correction is relatively seldom required, hence implemented in software. The
combination of DiskOnChip built-in EDC mechanism and the TrueFFS driver ensures highly reliable error detection
and correction, while providing maximum performance.
The following detection and correction capability is provided for each 512 bytes:
24
•
•
•
•
Programmable Boot Block with eXecute In Place (XIP) Capability
Block of 4KB.
Download Engine (DE)
Error Detection Code/Error Correction Code (EDC/ECC)
Corrects up to two 10-bit symbols, including two random bit errors.
Corrects single bursts up to 11 bits.
Detects single bursts up to 31 bits and double bursts up to 11 bits.
Detects up to 4 random bit errors.
Data Sheet, Rev. 1.7
DiskOnChip Millennium Plus 16/32/64MByte
93-SR-002-03-8L