AS3953 datasheet(38/71 Pages) AMSOSRAM

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[v1-05] 2019-Feb-15

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AS3953A − Detailed Description

Writing and Reading of EEPROM Through SPI

EEPROM data can be read and written also through SPI

interface. Due to possible conflict with RFID interface trying to

access the EEPROM in ISO 14443A - level4 mode, access is

granted to SPI only in case the PICC AFE is not active.

In all other modes defined in Mode Definition Registers, the

EEPROM can be accessed via SPI when the RF field is active.

Activity of the PICC AFE can be checked by observing hf_pon

bit of RFID Status Display Register. In case PICC AFE is activated

while the EEPROM writing or reading operation is going on, this

operation is interrupted, and l_ee_spi IRQ is sent.

Word Address Byte

Both EEPROM modes (Read and Write) use Word Address byte

to define the address of EEPROM word which is accessed. 7 MSB

bits of the Address Byte are used to define the address; while

the last bit is “don’t care” (utilized to synchronize EEPROM

access).

Note(s): The valid range for the Word Address byte is from 0000

000xb to 0011 111xb (EEPROM words from 00h to 1Fh).

Figure below defines the EEPROM Word Address byte.

Figure 45:

EEPROM Word Address Byte

EEPROM Write

In order to program an EEPROM word six bytes have to be sent

(mode byte, word address byte and 4 bytes of word data, all of

them MSB first)). Actual programming of EEPROM is started with

rising edge of /SS signal which terminated the EEPROM Write

command. During EEPROM programming the controller is not

allowed to start another SPI activity. Controller is informed

about the end of EEPROM programming by sending an

interrupt (an interrupt flag is set in the Auxiliary Interrupt

normally finished; in case of an error (writing to write protected

word, writing to non-existent address) an error flag (I_er_eew)

is set. Typical EEPROM programing time for one word is 8ms.

Note(s): Word data is sent MSB first which is opposite to RFID

EEPROM programming where LSB is sent first.

EEPROM Word

Address

WA6

WA5

WA4

WA3

WA2

WA1

WA0

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