ST25DV04KC datasheet(32/203 Pages) STMICROELECTRONICS

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5.3.1

I2C priority

When RF is in sleep mode or in off mode, RF commands are not interpreted, and RF cannot by busy. I2C is then

free to access the ST25DVxxKC exclusively.

Entering in RF sleep mode implies that I2C host writes into the RF_MNGT_Dyn register, which may not be

possible immediately if RF is busy.

In case I2C host needs to get exclusive and immediate access to the ST25DVxxKC, an immediate (or as soon as

possible) switch off (and on) of the RF interface is available.

A specific I2C “RFSwitchOff” command allows the I2C master to switch off RF immediately, or at the end of an RF

write in progress in EEPROM, even if an RF command is ongoing.

A specific I2C RFSwitchOn command allows the I2C master to switch on the RF immediately (RF returns to RF

mode defined by RF_MNGT_Dyn register).

Bit 5 of the I2C_CFG static register (I2C_RF_SWITCHOFF_EN) allows to enable or disable the RF switch off and

switch on from I2C.

The I2C “RFSwitchOff” command is defined as follow:

•

START condition, followed by the I2C “RFSwitchOff” salve address (1 Byte), followed by acknowledge bit

from the ST25DVxxKC, followed by STOP condition.

•

See Section 6.3 Device addressing for I2C RFSwitchOff slave address value explanation.

•

I2C “RFSwitchOff“ salve address is not acknowledged only if I2C_CFG register bit 5

(I2C_RF_SWITCHOFF_EN) is set to 0 and is always acknowledged otherwise (even if RF is busy).

Figure 15. I2C “RFSwitchOff” command

I2C DEVICE

CODE

ACK

R/W

0 0

The I2C RFSwitchOn command is defined as follow:

•

START condition, followed by I2C “RFSwitchOn” salve address (1 Byte), followed by acknowledge bit from

ST25DVxxKC, followed by STOP condition.

•

See Section 6.3 Device addressing for I2C RFSwitchOn slave address value explanation.

•

I2C “RFSwitchOn” salve address is not acknowledged only if I2C_CFG register bit 5

(I2C_RF_SWITCHOFF_EN) is set to 0 and is always acknowledged otherwise (even if RF is busy).

Figure 16. I2C “RFSwitchOn” command

I2C DEVICE

CODE

ACK

R/W

1 0

When ST25DVxxKC receives the I2C “RFSwitchOff” command outside of any RF command processing,

ST25DVxxKC is immediately setting the RF in off mode (see Section 5.2.2 RF management feature description).

If GPO interruption RF_OFF is enabled, a pulse is emitted on GPO pin after stop condition of the I2C

“RFSwitchOff” command.

When ST25DVxxKC receives the I2C “RFSwitchOff” command concurrently to an RF command, two possible

cases can happen:

ST25DV04KC ST25DV16KC ST25DV64KC

Interface arbitration

DS13519 - Rev 3

page 32/203

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