www.austriamicrosystems.com/HF_RFID_Reader/AS3910

Revision 2.3

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AS3910

Data Sheet - A p p l i c a t i o n I n f o r m a t i o n

Figure 6. Writing of Register Data with Auto-Incrementing Address

8.9.4 Reading of Data from Addressable Registers (READ Mode)

The command control Byte for a read command consists of a command code and an address. After the command code, the address of register

to be read has to be provided from the MSB to the LSB. Then one or more data bytes can be transferred from the SPI slave to the master, always

from the MSB to the LSB. As in case of the write command also the read command supports auto-incrementing address. To transfer bytes from

consecutive addresses, SPI master has to keep the SEN signal high and the SCLK has to be active as long as data need to be read from the

slave.

SDATAI is sampled at the falling edge of SCLK (like shown in the following diagrams), data to be read from the AS3910 internal register is driven

to SDATAO pin on rising edge of SCLK and is sampled by the master (μC) at the falling edge of SCLK.

A SEN LOW pulse has to be performed after register data has been transferred in order to indicate the end of the READ command and prepare

the Interface to the next command control Byte.

In case the register on defined address does not exist all 0 data is sent to SDATAO. Figure 7 illustrates an example for reading of a single byte.

Figure 7. Reading of a Single Register Byte

A5 A4 A3 A2 A1 A0 D7 D6 D5 D4D3 D2 D1 D0

X

0

0

X

SEN fall-

ing edge

signals

end of

WRITE

Mode

Data is moved to

Address

<A5-A0> + n

Two leading

Zeros indicate

WRITE Mode

SDATAI

SCLK

SEN

D7 D6 D5 D4 D3 D2 D1 D0 D7 D6

D1 D0 D7 D6 D5 D4 D3 D2 D1 D0

Data is moved to

Address

<A5-A0> + (n-1)

Data is moved to

Address

<A5-A0> + 1

Data is moved to

Address

<A5-A0>

A5

A4

A3

A2

A1

A0

D7

D6

D5

D4

D3

D2

D1

D0

X

SEN falling

edge signals

end of READ

Mode

SCLK

raising edge

Data is moved

from Address

<A5-A0>

SCLK

falling edge

Data is

transferred

to µC

SDATAI

SCLK

SEN

X

X

SDATAO

SCLK

falling edge

Data is sampled

SCLK raising

edge data is

transferred from

µC

01 pattern indi-

cates READ

Mode

1

0