Datasheet 249
Functional Description
5.24.4.3.1 SPI Flash Unlocking Requirements for Intel
®
Management Engine
Flash devices must be globally unlocked (read, write and erase access on the ME
region) from power on by writing 00h to the flash’s status register to disable write
protection.
If the status register must be unprotected, it must use the enable write status register
command 50h or write enable 06h.
Opcode 01h (write to status register) must then be used to write a single byte of 00h
into the status register. This must unlock the entire part. If the SPI flash’s status
register has non-volatile bits that must be written to, bits [5:2] of the flash’s status
register must be all 0h to indicate that the flash is unlocked.
If bits [5:2] return a non zero values, the Intel ME firmware will send a write of 00h to
the status register. This must keep the flash part unlocked.
If there is no need to execute a write enable on the status register, then opcodes 06h
and 50h must be ignored.
After global unlock, BIOS has the ability to lock down small sections of the flash as long
as they do not involve the Intel ME or GbE region.
5.24.4.4 Hardware Sequencing Requirements
Table 5-57 contains a list of commands and the associated opcodes that a SPI-based
serial flash device must support in order to be compatible with hardware sequencing.
Table 5-57. Hardware Sequencing Commands and Opcode Requirements
Commands Opcode Notes
Write to Status Register 01h
Writes a byte to SPI flash’s status register. Enable Write
to Status Register command must be run prior to this
command.
Program Data 02h
Single byte or 64 byte write as determined by flash part
capabilities and software.
Read Data 03h
Write Disable 04h
Read Status 05h Outputs contents of SPI flash’s status register
Write Enable 06h
Fast Read 0Bh
Enable Write to Status
Register
50h or
60h
Enables a bit in the status register to allow an update to
the status register
Erase
Program
mable
256B, 4 Kbyte, 8 Kbyte or 64 Kbyte
Full Chip Erase C7h
JEDEC ID 9Fh See Section 5.24.4.4.3.
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