Problems writing or reading password on Micron MT25QL256ABA NOR serial flash

[asuperman15]

Hi All!

Following are the proper codes for read and write the password in Micron MT25QL256ABA 

READ PASSWORD 27h

WRITE PASSWORD 28h

Write Enable is executed before to write password using 28H, I wait for the flash to be ready by reading the FLAG STATUS register, then I read the password to verify it was written properly.

The problem is that I am reading zeros only, and I do not understand why.

Perhaps, a step is missing, or a step sequence is required. Datasheet is not explaining or giving information about this topic. 

As a note, all the operations work as expected. I am able to erase, read/write data, read/write registers, etc, except by the password.

Here is the log: 

=============================================================
========== test_write_read_password ==========
=============================================================
========== Read Device ID
Device Id: 0x1019ba20

READ_SECTOR_PROTECTION_REG: 0x0000ffff
READ_GLOBAL_FREEZE_BIT_REG: 0x00000001
READ_VOLATILE_LOCK_BITS_REG: 0x00000000
READ_NONVOLATILE_LOCK_BITS_REG: 0x000000ff

========== Read Password
Password -> DATA 0: 0x00000000, DATA 1: 0x00000000
pwd0 = 0x00000000 pwd1 = 0x00000000

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00008827
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0x00000000
Flash Command Write 1 Register : 0x00000000
Flash Command Read 0 Register : 0x00000000
Flash Command Read 1 Register : 0x00000000

========== Write Enable

========== Write Password
Password -> DATA 0: 0xC0FFEE11, DATA1: 0xBABECAFF

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00008028
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc0ffee11
Flash Command Write 1 Register : 0xbabecaff
Flash Command Read 0 Register : 0x00000000
Flash Command Read 1 Register : 0x00000000

Flag Status 0x00000081

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00001870
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc0ffee11
Flash Command Write 1 Register : 0xbabecaff
Flash Command Read 0 Register : 0x00000081
Flash Command Read 1 Register : 0x00000000

========== Read Password
Password -> DATA 0: 0x00000000, DATA 1: 0x00000000

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00008827
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc0ffee11
Flash Command Write 1 Register : 0xbabecaff
Flash Command Read 0 Register : 0x00000000
Flash Command Read 1 Register : 0x00000000

========== Write Enable

========== Write Password
Password -> DATA 0: 0xC000FFEE, DATA1: 0xBABEBABE

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00008028
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc000ffee
Flash Command Write 1 Register : 0xbabebabe
Flash Command Read 0 Register : 0x00000000
Flash Command Read 1 Register : 0x00000000

Flag Status 0x00000081

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00001870
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc000ffee
Flash Command Write 1 Register : 0xbabebabe
Flash Command Read 0 Register : 0x00000081
Flash Command Read 1 Register : 0x00000000

========== Read Password
Password -> DATA 0: 0x00000000, DATA 1: 0x00000000

========== Read All Flash Registers
Control Register : 0x00000001
SPI Clock Baud Rate Register : 0x00000010
CS Delay Setting : 0x00000000
Read Capturing Register : 0x00000000
Operating Protocols Setting Register : 0x00000000
Read Instruction Register : 0x00000003
Write Instruction Register : 0x00007002
Flash Command Setting Register : 0x00008827
Flash Command Control Register : 0x00000000
Flash Command Address Register : 0x00000000
Flash Command Write 0 Register : 0xc000ffee
Flash Command Write 1 Register : 0xbabebabe
Flash Command Read 0 Register : 0x00000000
Flash Command Read 1 Register : 0x00000000