AS3955 datasheet(33/111 Pages) AMSCO

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ams Datasheet

Page 33

[v1-01] 2015-Apr-29

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AS3955 − Detailed Description

Figure 35:

CC Content at Delivery (2kbit Option)

Configuration Bytes

The Configuration bytes are used to define AS3955 operating

options. AS3955 is delivered by ams with default settings.

Authentication Password

The Authentication password block (bytes RFP0, RFP1, RFP2,

and RFP3) contains the 32-bit password. This password is used

for authentication over RF side. The NFC tag is set into

AUTHENTICATED state when a write command is issued via the

RF to write password address with the data that has same

content as the data stored in Authentication password block. If

the NFC tries to authenticate with a wrong password, AS3955

shall not respond and returns into SENSE / SLEEP state and the

value of the AUTH_CNT is decreased.

The password can be overwritten via RF only in

AUTHENTICATED state and can always be set via SPI / I²C.

Configuration register AUTH_CFG defines access rights

controlled by the password. The RF password can’t be read via

RF.

The authentication for read or write is required only to the

memory portion defined by AUTH_LIM. The chip is no longer in

AUTHENTICATED state when the tag leaves SELECTED state.

An attempt to read the password block will return zeroes. The

authentication does not override permissions set by the lock

bits. Authentication also does not restrict access over SPI / I²C

in any way.

Authentication can be configured using configuration bits in

AUTH_CFG and AUTH_LIM bytes.

Byte number in block

Block address

03h

E1h

10h

1Bh

00h

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