AS3911 datasheet(53/149 Pages) AMSCO

53 / 149 page

ams Datasheet, Confidential: 2013-Oct [2-03]

AS3911 – 53

Appl icatio n I n f o rm a t i o n

Figure 37:

Timing Parameters of NFC Field ON Commands

This command is accepted in case en (bit 7 of the Operation

Control Register) is set and Xtal oscillator frequency is stable.

Go to Normal NFC Mode

This command is used to transition from NFC target bit rate

detection mode to normal mode. Additionally it copies the

content of the NFCIP Bit Rate Detection Display Register to the

Bit Rate Definition Register and correctly sets the bit tr_am in

the Auxiliary Definition Register.

Analog Preset

This command is used to preset Receiver and Transmitter

configuration based on state of Bit Rate Definition Register and

Bit Rate Definition Register. Please note that no preset is done

in case Sub-carrier bits Stream or BPSK bit stream mode is

selected. The list of configuration bits that are preset is given

in Figure 38.

Figure 38:

Symbol

Parameter

Value

Unit

Note

TIDT

Initial delay time

4096

/fc

NFC Initial Field ON

TRWF

RF waiting time

512

/fc

TIRFG

Initial guard time

NFC Initial Field ON

TADT

Active delay time

768

/fc

NFC Response Field ON

TARFG

Active guard time

1024

/fc

NFC Response Field ON

Bit

Bit Name

Function

Address 02h: Operation Control Register

5rx_chn

1: one channel enabled

→ NFCIP-1 active communication (both initiator and target)

3tx_en

0: disable TX operation

→ NFCIP-1 active communication (both initiator and target)

Note: In case of any target mode or NFCIP-1 initiator mode bit tx_en is set to 0 to disable transmitter in case it

was enabled. In NFCIP-1 mode the switching on of the transmitter field is controlled by dedicated

commands.

Address 05h: ISO14443A and NFC 106kb/s Settings Register

nfc_f0

1: Add SB (F0) and LEN byte during Tx and skip SB (F0) byte during TX

→ NFCIP-1 active

communication (both initiator and target)

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