ST25R3920 datasheet(43/152 Pages) STMICROELECTRONICS

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DS13261 Rev 9

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ST25R3920

Application information

151

Bit d_ac_ap2p allows filtering of NFCIP-1 active frames.

Low power field detection

The Fixed listen communication and Bit rate detection modes can be enhanced in terms of

power consumption by using the field detector in Low-power mode, putting the ST25R3920

in power-down mode (en = 0) while waiting for an external field from a peer/reader.

For this mode the Bit rate detection mode or the Fixed listen communication mode have to

be selected, and bits en, rx_en and tx_en in the Operation control register need to be

cleared to 0.

In this mode the field detector has to be configured to automatic or manual peer detection

threshold.

On detection of external field (I_eon) the ST25R3920 temporarily enable the oscillator and

the receiver. The host needs to confirm it by setting en and rx_en option bits in the

Operation control register within 10 ms.

From this point on normal bit rate detection or normal target communication can be

performed.

PT memory

The PT_Memory is used to store data for NFCIP-1 passive target and NFC-A card/listen

mode. It is loaded via the host interface as described in Section 4.3.

Table 5. PT_Memory address space

Location

Description

Data usage

0-9

NFCID1 (4/7/RFU bytes)

4 bytes: locations 0-3

7 bytes: locations 0-6

NFC-A anticollision

10,11

SENS_RES2:1

SENS_REQ response

SELR_L1

SEL Level 1 response.

SELR_L2

SEL Level 2 response

SELR_L3

RFU

15,16

NFCF_SC

System code (SC) in SENSF_REQ(1)

1. SENSF_RES is transmitted in case received SC=NFCF_SC or SC=0xFFFF.

NFC-F anticollision

17-35

212/424 polling response SENSF_RES format(2)

2. NFC-212/424k SENS_RES format, see Table 6. The last two bytes in SENSF_RES are transmitted based

on the RC bytes in the SENSF_REQ.

36-47

TSN - Random numbers

Slot selection, 24 4-bit random

numbers are stored(3) (4)

3. The 4-bit slot numbers are sequentially used in the NFC212/424 Polling response. When only four TSN

numbers remain unused, an IRQ with I_sl_wl bit is sent.

4. Depending on the number of slots in the Polling request, appropriate number of the MSB bits in the slot

number is used.

Table 6. NFC-212/424k SENS_RES format

Byte 1

Bytes 2-9

Bytes 10-11

Bytes 12-14

Byte 15

Byte 16

Byte 17

Bytes 18-19

01h

NFCID2

PAD0

PAD1

MRTICHECK

MRTIUPDATE

PAD2

[RD]

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