How to modify BQ2084 default password?

There is a way, but you will need to use the Pro Screen rather than the data flash screen. You will need to know the locations of the current keys. The first key location is 0x00F8 for the first byte and 0x00F9 for the second  byte. The second key location is 0x00F6 for the first byte and 0x00F7 for the second byte. The procedure is as follows:

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PRO PAGE
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The four simple functions can be used to peek and poke data to the device. It is possible
to read and write to flash locations which are less than 0x100 using the following procedure:

To Read Data Flash...

1. Using the Write SMBus Word function, set hex address byte to 51, place the ADDRESS byte of the desired flash location in the hex data word box. Push the Write button

2. Using the Read SMBus Word function, set hex address byte to 52, push the read button.

To Write a Data Flash byte...

Using Write SMBus Word function, set hex address byte to 50, place the hex DATA byte for the desired flash byte location in the msb locations of the hex data word box. Place the desired ADDRESS byte of the flash data byte to write into the lsb part of the hex data word box. Push the Write button.

Here is an example:

To write DF using Pro Screen:

Write SMBus Word

          Address 0x50

          Data 0x23F6  (The 23 is the data you want to write and the F6 is the DF address location)

          Click Write

           Repeat for address locations 0xF7, 0xF8, and 0xF9.

To read DF using Pro Screen it is a two step process:

Write SMBus Word

          Address 0x51

          Data 0x00F6

          Write

Read SMBus Word

          Address 0x52

          Read (This will return the data in address location 0x00F6)