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AS3953

Datasheet - A pp l ic a t io n I n f or m a t i on

8.1.2 Reading of Data from Addressable Registers (Register Read Mode)

After the SPI operation mode bits the address of register to be read has to be provided from the MSB to the LSB. Then one or more data bytes

are transferred to MISO output, always from the MSB to the LSB. As in case of the write mode also the read mode supports auto-incrementing

address.

MOSI is sampled at the falling edge of SCLK (like shown in the following diagrams); data to be read from the AS3953 internal register is driven to

MISO pin on rising edge of SCLK and is sampled by the master at the falling edge of SCLK.

In case the register on defined address does not exist all ‘0’ data is sent to MISO.

In the following figure example for reading of single byte is given.

Figure 9. Reading of a Single Register

8.1.3 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 on page 31, 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.

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:

The valid range for the Word Address byte is from 0000 000xb to 0011 111xb (EEPROM words from 00h to 1Fh).

Table below defines the EEPROM Word Address byte.

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 Register).

I_eew flag is set in case EEPROM

programming is 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:

Word data is sent MSB first which is opposite to RFID EEPROM programming where LSB is sent first.

B7

B6

B5

B4

B3

B2

B1

B0

EEPROM Word Address

WA6WA5

WA4WA3

WA2WA1

WA0

x

00

1

A4

A3

A2

A1

A0

X

X

SCLK rising

edge Data is

moved from

Address

<A4-A0>

/SS rising

edge signals

end of READ

Mode

Three leading

bits indicate

Mode

D

4

D

3

D

2

D

1

D

0

D

7

D

6

X

X

SCLK rising

edge Data is

transfered

from µC

SCLK falling

edge Data is

sampled

SCLK falling

edge Data is

transfered to

µC

D

5

/SS

SCLK

MOSI

MISO