ST25R3918 datasheet(57/141 Pages) STMICROELECTRONICS

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DS13490 Rev 2

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ST25R3918

Application information

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

NFCIP-1 standard. See Figure 25 and Table 12 for details on the timing of these

commands.

Figure 25. Direct command NFC initial field ON

4.4.6

Mask receive data and Unmask receive data

The direct command Mask receive data disables processing of the receiver output by the

RX decoders, RSSI measurement, and AGC operation.

The direct command Unmask receive data enables processing of the received data by the

RX decoders, RSSI measurement and AGC operation. A common use of this command is

to re-enable the receiver operation after it was masked by the command Mask receive data.

If the Mask receive timer is still running while the direct command Unmask receive data is

received, reception is enabled, and the Mask receive timer is reset.

In passive target (card emulation) mode, the Unmask receive data command prepares the

RX decoders for a new data reception and clears the internal FDT timer. In passive target

mode, this direct command must be used only if no further transmission from the

ST25R3918 is planned and the device has to wait for the next command to be received.

4.4.7

Change AM modulation state

This command changes the AM modulation state from unmodulated to modulated, and vice

versa. This can be used to measure the AM modulation index with the direct command

MS42450V1

TIDT

TIRFG

n x TRFW

Start

RF on

TRFW

Table 12. Timing parameters of NFC field ON commands

Parameter

Symbol

Value

Unit

Notes

Initial delay time

TIDT

4096

/ fc

NFC initial field ON

RF waiting time

TRFW

512

/ fc

n = 0…3 based on nfc_n<1:0> in Auxiliary

definition register

Initial guard time

TIRFG

75 µs +

NFC field on guard time

NFC field on guard time defined in the NFC field

on guard timer register.

NFCIP-1 TIRFG requirement: 5 to 35 ms

Active guard time

TARFG

75 µs +

NFC field on guard time

NFC field ON guard time defined in the NFC

field on guard timer register.

NFCPIP-1 TARFG requirement:

> 75 µs + NFC field ON guard times (1024 / fc)

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