What’s New in the e•MMC™ 4.4 Spec?
The e•MMC 4.4 specification provides a host of new features that offer expanded functionality and security over e•MMC 4.3. Review our quick feature set comparison, or read on for brief descriptions of each of the new features.
Feature Comparison The e•MMC 4.4 spec offers a host of new features. Micron’s 4.4 parts even offer support for optional features like partitions and secure erase.
Partitions
Enables multiple general purpose partitions in the user data area. These partitions, or portions of partitions, can even be configured by the host (via one time program) as high performance (SLC) or high density (MLC), depending on application requirements. Creating these SLC partitions in MLC NAND eliminates the need for an extra SLC chip and reduces the component count—simplifying your BOM and product integration and freeing up board space.
Secure Write Protect
Allows either permanent or power-on write protect of a designated area, restricting access to the phone’s critical software, such as the boot code and operating system. In a power-on protected area, the write protect cannot be cleared without a hardware reset signal or power cycle. The host must reset protection after the desired operation is complete.
Secure Memory Block (Replay Protect Memory Block)
Allows one partition to be set to signed-only access for added data security. Any data transferred from/to this area must be sent with a message authentication code helping ensure that data is unaltered when transferred and stored.
Secure Erase
Enables complete purging of data from the physical memory array, ensuring that sensitive data like passwords and personal information can be securely erased.
Hardware Reset
A dedicated reset pin has been added, enabling access to areas protected by a power-on write protect (see secure write protect, above). It’s important to note that while some features can be implemented in firmware, HW reset cannot—it must be built into the e•MMC chip.
Right now, Micron is the only memory provider to offer fully compliant e•MMC 4.4 parts. We even go beyond the specification to include optional features like partition and secure erase.
Why HW Reset is Important for OS Storage
Note: partition size in graphic does not
indicate relative density.
The features built into the e-MMC 4.4 specification are designed to work together to provide added security and functionality. Together, the H/W reset and secure write protect features are the key to enabling a secure update of OS code stored in e-MMC memory.
To understand why, look at the partitioning differences diagram at right. In any application, the OS should be stored in a secure, write protected location to prevent malicious tampering or damage. The 4.3 specification does not have secure write protection, but 4.4 does. And, because the host cannot clear the secure protect with any MMC command, H/W reset is the only way to enable an OS update without a manual reboot (power cycle).
Don’t Settle for Less Than e•MMC 4.4
Several other e•MMC manufacturers have attempted to promote “e•MMC 4.3+” products that offer a partial feature set. The features of the 4.4 specification weren’t intended for this sort of piecemeal implementation. Don’t settle for less than the full e•MMC 4.4 compliance your application needs.