ST25R3916 datasheet(62/157 Pages) STMICROELECTRONICS

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Application information

ST25R3916/7

62/157

DS12484 Rev 4

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.

To determine whether an external field is present the ST25R3916/7 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 ST25R3916/7 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 ST25R3916/7 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 28, Figure 29 and Table 14

for details on the timing of these commands.

Figure 28. Direct command NFC initial field ON

MS42450V1

TIDT

TIRFG

n x TRFW

Start

RF on

TRFW

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