Data Protection In The Flash Card; Erase; Write Protection; Copy Bit - SanDisk SDSDB-32-201-80 - Industrial Grade Flash Memory Card Product Manual

Introduction to the SD Card

1.5.9.8. 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.

1.5.9.9. Erase

The smallest erasable unit in the SD Card is a sector. In order to speed up the erase procedure, multiple sectors can
be erased at the same time. To facilitate selection, a first command with the starting address is followed by a second
command with the final address, and all sectors within this range will be selected for erase.

1.5.9.10. Write Protection

Two-card level write protection options are available: permanent and temporary. Both can be set using the
PROGRAM_CSD command (see below). The permanent write protect bit, once set, cannot be cleared. This feature
is implemented in the SD Card controller firmware and not with a physical OTP cell.
NOTE: Use the Write Protect (WP) Switch located on the card's side edge to prevent the host from writing to or
erasing data on the card. The WP switch does not have any influence on the internal Permanent or
Temporary WP bits in the CSD.

1.5.9.11. Copy Bit

The content of a SD Card 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 SD Card is programmed (during test and
formatting on the manufacturing floor) as a copy. The SD Card can be purchased with the copy bit set (copy) or
cleared, indicating the card is a master. This feature is implemented in the SD Card controller firmware and not with
a physical OTP cell.

1.5.9.12. The CSD Register

All the configuration information of the SD Card is stored in the CSD register. The MSB bytes of the register
contain manufacturer data and the two least significant bytes contain the host-controlled data, the card Copy, write
protection and the user file format indication.
The host can read the CSD register and alter the host controlled data bytes using the SEND_CSD and
PROGRAM_CSD commands.
1.5.10. SD Card—SPI Mode
The SPI mode is a secondary communication protocol for SD Cards. This mode is a subset of the SD Card protocol,
designed to communicate with an SPI channel, commonly found in Motorola's (and lately a few other vendors')
microcontrollers.
1-10 SanDisk Secure Digital (SD) Card Product Manual, Rev. 1.9 © 2003 SANDISK CORPORATION