ST25DV04K datasheet(73/200 Pages) STMICROELECTRONICS

73 / 200 page

Following a Start condition, the bus master sends a device select code with the Read/ Write bit (R W ) reset to

0 and the Chip Enable bit E2 at 1. The device acknowledges this, as shown in Figure 31. I2C Write Password

Sequence, and waits for the two I2C password address bytes, 09h and 00h. The device responds to each address

byte with an acknowledge bit, and then waits for the four password data bytes, the validation code, 07h, and a

resend of the eight password data bytes. The most significant byte of the password is sent first, followed by the

least significant bytes.

It is necessary to send twice the 64-bit password to prevent any data corruption during the write sequence. If the

two 64-bit passwords sent are not exactly the same, the ST25DVxxx does not modify the I2C password value.

When the bus master generates a Stop condition immediately after the Ack bit (during the tenth bit time slot), the

internal write cycle is triggered. A Stop condition at any other time does not trigger the internal write cycle.

During the internal write cycle, the serial data (SDA) signal is disabled internally, and the device does not respond

to any requests.

Caution:

I2C write password command data transits via the 256-Bytes fast transfer mode's buffer. Consequently fast

transfer mode must be deactivated before issuing a write password command, otherwise command is NotACK

(after address LSB), and programming is not done and device goes in standby mode.

Figure 31. I2C Write Password Sequence

Device

select code

Password

[63:56]

Ack

R/W

Ack

Device select code = 1010111

Ack generated during 9th bit time slot.

Ack

Password

[55:48]

Password

[47:40]

Password

[39:32]

Password

[23:16]

Password

[15:08]

Password

[7:0]

Ack

Password

[23:16]

Password

[15:08]

Password

[7:0]

Password

[63:56]

Password

[55:48]

Password

[47:40]

Password

[39:32]

Password

Address 00h

Password

Address 09h

Validation

code 07h

Ack

Password

[31:24]

Ack

Password

[31:24]

ST25DV04K ST25DV16K ST25DV64K

I2C password management

DS10925 - Rev 9

page 73/200

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