SL3ICS1002F7AF datasheet(34/51 Pages) NXP

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139037

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Product data sheet

COMPANY PUBLIC

Rev. 3.7 — 9 October 2012

139037

34 of 51

NXP Semiconductors

SL3ICS1002/1202

UCODE G2XM and G2XL

14.12.3 ChangeEAS

A G2X equipped RFID tag can be enhanced by a stand-alone operating EAS alarm

feature. With an EAS-Alarm bit set to '1' the tag will reply to an EAS_Alarm command by

backscattering a 64 bit alarm code without the need of a Select or Query. The EAS is a

built-in solution so no connection to a backend database is required. As it is a custom

command no Select or Query is required to detect the EAS state enabling fast, reliable

and offline article surveillance.

ChangeEAS can be executed from the Secured state only. The command will be ignored

if the Access Password is zero, the command will also be ignored with an invalid CRC-16

or an invalid handle, the G2X will than remain in the current state. The CRC-16 is

calculated from the first command-code bit to the last handle bit. A frame-sync must be

prepended the command.

The G2X reply to a successful ChangeEAS will use the extended preamble, as

appropriate (i.e. a Tag shall reply as if TRext=1) regardless of the TRext value in the

Query that initiated the round.

After sending a ChangeEAS an interrogator shall transmit CW for less than TReply or

20 ms, where TReply is the time between the interrogator's ChangeEAS command and

the G2X backscattered reply. An interrogator may observe three possible responses after

sending a ChangeEAS, depending on the success or failure of the operation

• Write succeeds: After completing the ChangeEAS a G2X will backscatter the reply

shown in Table 22 comprising a header (a 0-bit), the handle, and a CRC-16 calculated

over the 0-bit and handle. If the interrogator observes this reply within

20 ms then the ChangeEAS completed successfully.

• The G2X encounters an error: The G2X will backscatter an error code during the CW

period rather than the reply shown in Table 22 (see EPCglobal Spec for error-code

definitions and for the reply format).

• Write does not succeed: If the interrogator does not observe a reply within 20 ms then

the ChangeEAS did not complete successfully. The interrogator may issue a Req_RN

command (containing the handle) to verify that the G2X is still in the interrogator's

field, and may reissue the ChangeEAS command.

Upon receiving a valid ChangeEAS command a G2X will perform the commanded

set/reset operation of the EAS_Alarm-Bit.

If EAS-Bit is set, the EAS_Alarm command will be available after the next power up and

reply the 64 bit EAS code upon execution. Otherwise the EAS_Alarm command will be

ignored.

Table 20.

ChangeEAS command

Command

ChangeEas

CRC-16

# of bits

description

11100000

00000011

1 ... set EAS system bit

0 ... reset EAS system bit

handle

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