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[v1-11] 2018-Nov-14

AS3956 − Detailed Description

SLEEP State

Together with SENSE state, SLEEP state is the other waiting state

for AS3956. SLEEP state can be entered upon reception of a SLP_

REQ command. The distinction between SENSE and SLEEP state

is made necessary to discriminate selected and not yet selected

tags.

AS3956 can only exit this state upon reception of an ALL_REQ

command. Any other command received in this state is

interpreted as an error and AS3956 state remains unchanged.

RESOLUTION State

In RESOLUTION state, the NFC device is resolving the tag UID.

Since AS3956 has a double size UID, the RESOLUTION state

actually comprises of two sub-states, where the anti-collision

procedure is carried out in Cascade Level 1 and 2. Please refer

to [ISO18092] for further information.

SELECTED State

All memory operations are operated in SELECTED state.

Upon reception of a SLP_REQ command, SELECTED state is

exited and AS3956 transits to SLEEP state. Any other command

received when the device is in this state is interpreted as an

error. Depending on its previous state, AS3956 returns to either

SENSE or SLEEP state.

Upon reception of a SECTOR SELECT command, AS3956 returns

a NAK and transits to SENSE or SLEEP state, depending on its

previous state.

AS3956 transits to the AUTHENTICATED state after successful

password verification, using a standard WRITE command to a

dedicated memory address (see Authentication Password). The

number of permitted failed authentications is set to 7, after

which AS3956 transits to LOCKED sub-state (not shown in the

picture). When LOCKED state is entered, only the MCU can bring

AS3956 back to SENSE state by resetting the authentication

counter (Configuration Byte AUTH_CNT) back to 0 and issue a

Set Default, or Go To Sense, or Go To Sleep command.

When in LOCKED sub-state, all memory operations are only

allowed in the memory area not password protected, as defined

by the configuration byte Configuration Byte AUTH_LIM.

Upon reception of a SLP_REQ command, SELECTED state is

exited and AS3956 transits to SLEEP state.

Any other command received when the device is in this state is

interpreted as an error and, depending on its previous state,

AS3956 returns to either SENSE or SLEEP state.

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