ST25R3916B datasheet(64/165 Pages) STMICROELECTRONICS

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Application information

ST25R3916B ST25R3917B

64/165

DS13541 Rev 7

The direct commands Transmit REQA and Transmit WUPA automatically disable the CRC

check of the response frame. The CRC check is enabled again after any of the below

conditions:

•

Transmit with CRC direct command

•

Mask receive data direct command

•

No Response timer expires

If the direct command Transmit without CRC is used in Felica™ mode the Length and CRC

bytes are skipped. After the preamble and Sync bytes the raw FIFO content is transmitted.

A transmit length nbtx<2:0> ≥1 must be used.

4.4.5

NFC field ON commands

The NFC field ON direct commands are used to perform RF Collision Avoidance. The

external field detector must be enabled for these commands to work correctly.

Note:

It is recommended that bits en_fd_c<1:0> of the operation control register are set to 01b in

Reader mode. In the NFCIP-1 active communication (AP2P), the bits en_fd must be set to

11b to enable an external field detector automatically. So that the external field detector

automatically exchanges its threshold between collision avoidance and peer detection level,

as needed, during operation. Collision avoidance and peer detection levels must be tuned

(in accordance with environmental temperature) to ensure good working conditions. In

AP2P mode, a minimum collision avoidance and peer detection activation threshold of

205 mVPP is recommended for bits rfe_t<3:0> and trg_l<3:0> of the external field detector

activation threshold register.

To determine whether an external field is present the ST25R3916B and ST25R3917B

compares the RF voltage level on the RFI1 pin with the collision avoidance threshold

defined in the External field detector activation threshold register.

If no external field is detected, then the ST25R3916B and ST25R3917B transmitter is

switched on automatically (bit tx_en in the Operation control register is set) and an I_apon

IRQ is signaled. After the RF guard time defined in the NFC field on guard timer register has

passed an I_cat IRQ is signaled. At this point the controller can initiate a data transmission

using a transmit command.

If an external field is detected a I_cac IRQ is signaled, and the ST25R3916B and

ST25R3917B transmitter stays off.

The direct command NFC initial field ON performs an Initial collision avoidance according to

NFCIP-1 standard, and the direct command NFC response field ON performs a Response

collision avoidance according to NFCIP-1 standard. See Figure 30, Figure 31 and Table 15

for details on the timing of these commands.

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