AS3909 datasheet(30/77 Pages) AMSCO

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AS3909/AS3910 – 30

ams Datasheet, Confidential: 2013-Oct [3-02]

A p pl i c at io n I n f o r m at i o n

Clear

This direct command stops all current activities (transmission

or reception) and clears FIFO. It also clears Collision and

Interrupt Registers. This command has to be sent first in a

sequence preparing a transmission (except in case of direct

commands Transmit REQA and Transmit WUPA).

Transmit Commands

All Transmit commands (Transmit with CRC, Transmit without

CRC, Transmit REQA and Transmit WUPA) are only accepted in

case the Transmitter is enabled (bit tx_en is set).

NFC Transmit Commands

The NFC transmit commands (NFC transmit with Initial RF

Collision Avoidance, NFC transmit with Response RF Collision

Avoidance, NFC transmit with Response RF Collision Avoidance

with n=0) are used to transmit requests and responses in the

NFC mode. Before actual transmission the RF Collision

avoidance with Collision avoidance threshold defined in the

NFCIP Field Detection Threshold Register is performed.

In the command NFC transmit with Response RF Collision

Avoidance n is randomly set in a range from 0 to 3, while in the

command NFC transmit with Response RF Collision Avoidance

with n=0 it is set to 0. In case collision is detected during the RF

Collision Avoidance the transmission is not done and an

interrupt is sent with flag INTR due to NFC event.

The NFC transmit commands switch on and off the transmission

block, setting the Operation control bit tx_en in the NFC mode

is not allowed.

Timing of the NFC transmit commands is according to the

ISO/IEC 18092 standard. For some timings the ISO/IEC 18092

specifies a range.

Figure 21:

NFC P2P Timings Implemented in AS3909/10

Symbol

Parameter

Value

Unit

Note

TIDT

Initial delay time

302

μs

Initial RF Collision Avoidance

TRWF

RF waiting time

37.76

μs

TIRFG

Initial guard time

5.11

Initial RF Collision Avoidance

TADT

Active delay time

151

μs

Response RF Collision Avoidance

TARFG

Active guard time

μs

Response RF Collision Avoidance

TGAS

Guard time after sending

response or request

μs

TGAS is the time during which RF field stays

switched on after sending a response or

request. This time is not specified in the

ISO/IEC 18092.

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