Partial Permanent Write Protection for Memory Card Segments
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Solution Overview
Problem
The existing Multimedia Card (MMC) specification does not allow for partial permanent write protection of a memory card, where important information can be protected while still allowing user access to other parts of the card, as existing methods either protect the entire card or none of it.
Innovation Solution
Defining a bit in the CSD register to set permanent write protection for specific segments of the card, using new commands like SET_PERM_WRITE_PROT and PARTIAL_PERM_WP to ensure that only certain parts are permanently write-protected, allowing other parts to remain accessible for user data storage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the entire memory card is permanently write protected, then critical data is protected from deletion, but user access to other parts of the card is restricted
Solution Approach 1:
The memory card is divided into multiple write protect groups (WP_GRP), each independently controllable through the CSD register's WP_GRP_SIZE field. This segmentation allows selective write protection of specific portions while leaving other portions accessible for user operations, resolving the contradiction between protecting critical data and maintaining user access capability.
Solution Approach 2:
Different regions of the memory card are assigned different write protection states locally. The CSD register configuration enables certain WP_GRP to be permanently write protected while other WP_GRP remain writable, allowing each region to have quality (protection status) tailored to its specific data requirements.
2Reliability
If write protection is applied to a portion of the memory card, then critical data is protected, but the protection can be accidentally cancelled
Solution Approach 1:
The PERM_WRITE_PROTECT bit in the CSD register is set in advance to establish permanent write protection status. This preliminary configuration ensures that once write protection is applied to specific WP_GRP, it cannot be accidentally removed by standard CLR_WRITE_PROTECT commands, preventing accidental deletion of protected data.
Solution Approach 2:
The PERM_WRITE_PROTECT bit acts as a preliminary countermeasure against accidental protection removal. By setting this bit, the system pre-establishes a barrier that prevents the harmful action (accidental deletion) from occurring, even if the user attempts to use protection cancellation commands.
3Reliability
If the memory card uses only ROM technology, then data is permanently protected, but user data storage and modification are limited
Solution Approach 1:
The memory card combines ROM and RW technologies in separate WP_GRP segments. The ROM portion provides permanent protection for critical data, while the RW portion allows flexible user data storage and modification, enabling the card to serve multiple functions simultaneously.
Solution Approach 2:
The memory card employs a composite structure combining ROM (for permanent protection) and RW memory technologies (for flexible storage). This composite approach allows the card to simultaneously provide permanent data protection and user-friendly storage flexibility, resolving the contradiction between reliability and adaptability.
Data Source
AI summary
This invention relates to a method permanently write protecting a portion of a memory card. According to the invention a bit indicating permanent write protection or permanent write protection of a portion of the memory card is set in the specific data register of the memory card to indicate that all the write protect groups protected with write protecting command are permanently write protected. In another embodiments of the invention special commands are used to control the write protection of the portion of the memory card. This invention also relates to a partially permanently write protected memory card. The invention further relates to an electronic device, a software, a system and a module utilizing the method of the invention.