MultiMediaCardTM
2.6.7 Data Protection in the Flash Card
Every sector is protected with an Error Correction Code (ECC). The ECC is generated (in the memory
card) when the sectors are written and validated when the data is read. If defects are found, the data is
corrected prior to transmission to the host.
The MultiMediaCard can be considered error free and no additional data protection is needed.
However, if an application uses additional, external, ECC protection, the data organization is defined in
the user writeable section of the CSD register
2.6.8 Erase
The smallest erasable unit in the MultiMediaCard is a erase group. In order to speed up the erase
procedure, multiple erase groups can be erased in the same time. The erase operation is divided into
two stages.
Tagging - Selecting the Sectors for Erasing
To facilitate selection, a first command with the starting address is followed by a second command with
the final address, and all erase groups within this range will be selected for erase.
Erasing - Starting the Erase Process
Tagging can address erase groups. An arbitrary selection of erase groups may be erased at one time.
Tagging and erasing must follow a strict command sequence (refer to the MultiMediaCard standard
specification for details).
2.6.9 Write Protection
The MultiMediaCard erase groups are grouped into write protection groups. Commands are provided
for limiting and enabling write and erase privileges for each group individually. The current write protect
map can be read using SEND_WRITE_PROT command.
In addition two, permanent and temporary, card levels write protection options are available.
Both can be set using the PROGRAM_CSD command (see below). The permanent write protect bit,
once set, cannot be cleared.
The One Time Programmable (OTP) characteristic of the permanent write protect bit is implemented in
the MultiMediaCard controller firmware and not with a physical OTP cell.
2.6.10 Copy Bit
The content of an MultiMediaCard can be marked as an original or a copy using the copy bit in the
CSD register. Once the Copy bit is set (marked as a copy) it cannot be cleared.
The Copy bit of the MultiMediaCard is programmed (during test and formatting on the manufacturing
floor) as a copy. The MultiMediaCard can be purchased with the copy bit set (copy) or cleared,
indicating the card is a master.
The One Time Programmable (OTP) characteristic of the Copy bit is implemented in the
MultiMediaCard controller firmware and not with a physical OTP cell.
2.6.11 The CSD Register
All the configuration information of the MultiMediaCard is stored in the CSD register. The MSB bytes of
the register contain manufacturer data and the two least significant bytes contains the host controlled
data - the card Copy and write protection and the user ECC register.
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