ST25DV64K datasheet(72/200 Pages) STMICROELECTRONICS

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Sequential read in dynamic registers:

•

There is no roll over at the end of the mailbox (ST25DVxxx returns only FFh after last system memory byte

address).

6.5.4

Acknowledge in Read mode

For all Read commands, the device waits, after each byte read, for an acknowledgement during the ninth bit time.

If the bus master does not drive serial data (SDA) low during this time, the device terminates the data transfer and

switches to its Standby mode.

6.6

I2C password management

The ST25DVxxx controls I2C security session using an I2C 64-bit password. This I2C password is managed with

two I2C dedicated commands: I2C present password and I2C write password.

6.6.1

I2C present password command description

The I2C present password command is used in I2C mode to present the password to the ST25DVxxx. This is

used to open I2C security session or to allow I2C password modification (see Section 5.6 Data Protection for

detailed explanation about password usage).

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 30. I2C Present Password

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

byte with an acknowledge bit, and then waits for the eight password data bytes, the validation code, 09h, 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 the 64-bit password twice to prevent any data corruption during the sequence. If the two

64-bit passwords sent are not exactly the same, the ST25DVxxx does not start the internal comparison.

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

ST25DVxxx compares the 64 received data bits with the 64 bits of the stored I2C password. If the values match,

the I2C security session is open, and the I2C_SSO_Dyn register is set to 01h. If the values do not match, the I2C

security session is closed and I2C_SSO_dyn register is set to 00h.

I2C_SSO_Dyn is a Dynamic register, it can be checked via I2C host to know If I2C security session is open.

Figure 30. I2C Present 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

[31:24]

Password

[23:16]

Password

[15:8]

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 09h

Ack

Password

[7:0]

Ack

Password

[31:24]

6.6.2

I2C write password command description

The I2C write password command is used to update the I2C password value (register I2C_PWD). It cannot be

used to update any of the RF passwords. After the write cycle, the new I2C password value is automatically

activated. The I2C password value can only be modified after issuing a valid I2C present password command.

ST25DV04K ST25DV16K ST25DV64K

I2C password management

DS10925 - Rev 9

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