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AS3953

Datasheet - D e t a il e d D es c r i pt io n

If configuration

bit15 [nfc] is set to logic ‘1’, the SAK on Cascade Level 2 reports that tag is NFC passive target (see table below).

ATS.

ATS is response to ISO 14443-4 command

RATS. The content of the ATS is used to inform the PCD about PICC capability (like the maximum

frame size, support of higher bit rates, etc.)

Several response fields of ATS are stored in EEPROM configuration word. The AS3953 ATS is composed of following 5 bytes according to

[ISO4]: TL, T0, TA(1), TB(1) and TC(1).



TL: This is the length byte. Since ATS is composed of 5 bytes, its content is 0x05. Table below defines the coding of the TL byte.



T0: This is the format byte. Table below defines the coding of the T0 byte.

Bit

b8 is set to ‘0’.

Bits

b7 to b5 indicate presence of bytes TA(1), TB(1) and TC(1) and hence are all set to ‘1’.

Bits

b4 to b1 are called FCSI and codes FCS. The FCS is maximum size of a frame defined by PICC. It is defined by configuration bits fsci<3:0>.



TA(1): This codes the bit rate capability of PICC. Supported higher bit rates of AS3953 are 212, 424 and 848 kb/s. However in specific

applications, it is advised to report lower capability to PCD (for example, due to the usage of slow controller or low power application). Due

to this reason the TA(1) response is configurable using configuration bits.

Bit

b8 set to ‘0’ codes possibility of having different data rates for each direction.



TB(1): The interface byte TB(1) conveys information to define the frame waiting time and the start-up frame guard time. The interface byte

TB(1) consists of two parts:

- The most significant half-byte

b8 to b5 is called FWI and codes frame waiting time (FWT).

- The least significant half byte

b4 to b1 is called SFGI and codes a multiplier value used to define the SFGT. The SFGT defines a specific

guard time needed by the PICC before it is ready to receive the next frame after it has sent the ATS. SFGI is coded in the range from 0 to

14. The value of ‘0’ indicates ‘No SFGT needed’.

The SFGT bits are fixed to default value which is 0x0, while the FWI bits are defined by configuration bits

fwi<3:0>. Table below defines the

coding of the TB(1) byte.

b8

MSB

b7

b6

b5

b4

b3

b2

b1

LSB

Description

0

1

0

00000

UID complete, tag is compliant to

NFCIP-1 transport protocol

b8

MSB

b7

b6

b5

b4

b3

b2

b1

LSB

Description

0

0

0

0

0

1

0

1

Coding of ATS byte TL

b8

MSB

b7

b6

b5

b4

b3

b2

b1

LSB

Description

0

1

1

1

fsci<3>

fsci<2>

fsci<1>

fsci<0>

Coding of ATS byte T0

TC(1)

TB(1)

TA(1)

FCSI

b8

MSB

b7

b6

b5

b4

b3

b2

b1

LSB

Description

dr_sdr

dr_picc_8

dr_picc_4

dr_picc_2

0

dr_pcd_8

dr_pcd_4

dr_pcd_2

Coding of ATS byte TA(1)

DS (PICC to PCD)

DR (PCD to PICC)

b8

MSB

b7

b6

b5

b4

b3

b2

b1

LSB

Description

fwi<3>

fwi<2>

fwi<1>

fwi<0>

0

0

0

0

Coding of ATS byte TB(1)

FWI

SFGI