ST25DV04K datasheet(25/197 Pages) STMICROELECTRONICS

25 / 197 page

Adding a message is only possible when fast transfer mode is enabled (MB_EN=1) and mailbox is free

(HOST_PUT_MSG and RF_PUT_MSG cleared, which is the case after POR or after complete reading of I2C

message by RF, and complete reading of RF message by I2C).

A watchdog limits the message availability in time: when a time-out occurs, the mailbox is considered free, and

the HOST_MISS_MSG or RF_MISS_MSG bits is set into MB_CTRL_Dyn register. The data contained in the

mailbox is not cleared after a read or after the watchdog has been triggered: message data is still available

for read and until fast transfer mode is disabled. HOST_CURRENT_MSG and RF_CURRENT_MSG bits are

indicating the source of the current data.

The message is stored in a buffer (256 Bytes), and the write operation is done immediately. .

Caution:

The data written in user or system memory (EEPROM), either from I2C or from RF, transits via the 256-Bytes

fast transfer mode's buffer. Consequently fast transfer mode must be deactivated (MB_EN=0) before starting

any write operation in user or system memory, otherwise command will be NotACK for I2C or get an answer 0Fh

for RF and programming is not done.

I2C access to mailbox

The access by I2C can be done by dedicated address mapping to mailbox (2008h to 2107h) with device identifier

E2 = 0.

I2C reading operation does not support rollover. Therefore data out is set to FFh when the counter reaches the

message end.

The RF_PUT_MSG is cleared after reaching the STOP consecutive to reading the last message byte, and the

mailbox is considered free (but the message is not cleared and it is still present in the mailbox).

A I2C reading operation will never clear HOST_PUT_MSG, and the message remains available for RF.

An I2C read can start at any address inside the mailbox (between address 2008h and 2107h).

A I2C write operation must start from the first mailbox location, at address 2008h. After reaching the Mailbox

border at address 2107h all bytes are NACK and the command is not executed (rollover feature not supported).

At the end of a successful I2C message write, the message length is automatically set into MB_LEN_Dyn register,

and HOST_PUT_MSG bit is set into MB_CTRL_Dyn register, and the write access to the mailbox is not possible

until the mailbox has been released again. MB_LEN_Dyn contains the size of the message in byte, minus 1.

RF access to mailbox

The RF Control & Access to mailbox is possible using dedicated custom commands:

•

Read Dynamic Configuration and Fast Read Dynamic Configuration to check availability of mailbox.

•

Write Dynamic Configuration and Fast Write Dynamic configuration to enable or disable fast transfer mode.

•

Read Message Length and Fast Read Message Length to get the length of the contained message,

•

Read Message and Fast Read Message to download the content of the mailbox,

•

Write Message and Fast Write Message to put a new message in mailbox. (New length is automatically

updated after completion of a successful Write Message or Fast Write Message command).

HOST_PUT_MSG is cleared following a valid reading of the last message byte, and mailbox is considered free

(but message is not cleared and is still present in the mailbox).

A RF read can start at any address of inside the message, but return an error 0Fh if trying to read after the last

byte of the message.

A RF reading operation will never clear RF_PUT_MSG , the message will remain available for I2C.

At the end of a successful RF message write, the message length is automatically set in MB_LEN_Dyn register,

and RF_PUT_MSG bit is set in MB_CTRL_Dyn register. and write access to the mailbox is not possible until

mailbox has been freed again.

The presence of a DC supply is mandatory to get RF access to the mailbox. VCC_ON can be checked reading

the dynamic register EH_CTRL_Dyn.

To get more details about sequences to prepare and initiate a Fast Transfer, to detect progress of a fast transfer

or to control and execute a fast transfer, please refer to AN4910. How to exchange data between wired (I2C) and

wireless world (RF ISO15693) using fast transfer mode supported by ST25DVxxx).

ST25DV04K ST25DV16K ST25DV64K

Fast transfer mode (FTM)

DS10925 - Rev 11

page 25/197

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