ST25DV04KC datasheet(69/203 Pages) STMICROELECTRONICS

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6.3

Device addressing

To start a communication between the bus master and the slave device, the bus master must initiate a Start

condition. Following this, the bus master sends the device select code, shown in Section B.1 Device select

codes (on serial data (SDA), the most significant bit first).

The device select code consists of a 4-bit device type identifier (I2C_DEVICE_CODE) and a 3-bit Chip Enable

“Address” (E2, E1, E0). Chip Enable bits E2 and E1 are used to select ST25DVxxKC memory to address (user or

system) and to send special I2C "RFSwitchOff"and I2C "RFSwitchOn" commands.

The eighth bit is the Read/Write bit (RW). It is set to 1 for Read and to 0 for Write operations. Refer to the table

below.

Table 89. Device select code

ST25DvxxKC function

I2C device type identifier

R/notW

Bit 7

Bit 6

Bit 5

Bit 4

Bit 3

Bit 2

Bit 1

Bit 0

User memory

I2C_DEVICE_CODE[3:0]

I2C_E0

1/0

System memory

1/0

I2C RFSwitchOff

I2C RFSwitchOn

The 4-bit device type identifier and the Chip Enable bit E0 are configurable though the I2C_CFG static register.

Table 90. I2C_CFG access

I2C

Command

Type

Address

Type

No access

E2=1, E1=1, 000Eh

R always, W if I2C security session is open

Table 91. I2C_CFG

Bit

Name

Function

Factory value

b3-b0

I2C_DEVICE_CODE

Device code (bits [7:4]) of I2C slave address

1010b

I2C_E0

E0 bit (bit 1) of I2C slave address

I2C_RF_SWITCHOFF_EN

0: I2C cannot switch off/on RF with I2C « RFSwitchOff/On » commands.

1: I2C can switch off/on RF with i2C « RFSwitchOfff/On » commands

b7-b6

RFU

00b

Note:

Refer to Table 13. System configuration memory map for the UID register.

Change in I2C_CFG command is immediate after STOP condition of the I2C write to this register. Next I2C

accesses shall use the new value of I2C_DEVICE_CODE and I2C_E0 to address the ST25DVxxKC.

If a match occurs on the device select code, the corresponding device gives an acknowledgement on serial data

(SDA) during the ninth bit time. If the device does not match the device select code, it deselects itself from the

bus, and goes into Standby mode.

ST25DV04KC ST25DV16KC ST25DV64KC

Device addressing

DS13519 - Rev 3

page 69/203

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