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 30 of 48
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 17
.
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 17
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 17
(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
