139037 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2013. All rights reserved.
Product data sheet
COMPANY PUBLIC
Rev. 3.8 — 11 November 2013
139038 32 of 48
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 20
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 20
(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 18. ChangeEAS command
Command ChangeEas RN CRC-16
# of bits 16 1 16 16
description 11100000
00000011
1 ... set EAS system bit
0 ... reset EAS system bit
handle
