SL3ICS1002F7AF datasheet(32/51 Pages) NXP

32 / 51 page

139037

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Product data sheet

COMPANY PUBLIC

Rev. 3.7 — 9 October 2012

139037

32 of 51

NXP Semiconductors

SL3ICS1002/1202

UCODE G2XM and G2XL

14.12.2 Reset ReadProtect

Reset ReadProtect allows an interrogator to resets the ReadProtect-bit and re-enables

reading of the G2X memory content according the EPCglobal specification.

The G2X will execute Reset ReadProtect from the Open or Secured states.

If a G2X in the Open or Secured states receives a Reset ReadProtect with a valid CRC-16

and a valid handle but an incorrect access password, it will not reply and transit to the

Arbitrate state.

If a G2X in the Open or Secured states receives a Reset ReadProtect with a valid CRC-16

and a valid handle but the ReadProtect-Bit is not set ('0'), it will not change the

ReadProtect-Bit but backscatter the reply shown in Table 19.

If a G2X in the Open or Secured receives a Reset ReadProtect with a valid CRC-16 but

an invalid handle, or it receives a Reset ReadProtect before which the immediately

preceding command was not a Req_RN, it will ignore the Reset ReadProtect and remain

in its current state.

A frame-sync must be prepended the Reset ReadProtect command.

After sending a Reset ReadProtect an interrogator shall transmit CW for the lesser of

TReply or 20 ms, where TReply is the time between the interrogator's Reset ReadProtect

command and the G2X backscattered reply. An interrogator may observe three possible

responses after sending a Reset ReadProtect, depending on the success or failure of the

operation:

• Write succeeds: After completing the Reset ReadProtect a G2X will backscatter the

reply shown in Table 19 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 Reset ReadProtect 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 19 (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 Reset ReadProtect did not complete successfully. The interrogator may issue a

Req_RN command (containing the handle) to verify that the G2X is still in the

interrogation zone, and may reissue the Reset ReadProtect command.

The G2X reply to the Reset ReadProtect command will use the extended preamble shown

in EPCglobal Spec (Figure 6.11 or Figure 6.15), as appropriate (i.e. a G2X will reply as if

TRext=1 regardless of the TRext value in the Query that initiated the round.

The Reset ReadProtect command is structured as following:

• 16 bit command

• Password: 32 bit Access-Password XOR with 2 times current RN16

• 16 bit handle

• CRC-16 calculate over the first command-code bit to the last handle bit

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