NXP Semiconductors

SL3S1005

UCODE 9xm

9.6.3 Untraceable

The EPC Gen2v2.1 Untraceable command allows the UCODE 9xm to hide the complete or parts of the EPC,

TID and/or user memory. In addition, the read range can be completely or temporarily reduced.

This command can only be executed from the secured state.

Memory parts which are set untraceable are acting as non-existing.

EPC-field:

Specifies the number of words of the EPC memory which the UCODE 9xm back scatters. A change of this field

therefore also changes the L bit in the Protocol Control (PC) word.

TID-field:

Hide some ("01") hides the TID memory from address 20h (included) onwards.

Range-field:

In case of activated range toggling, the read range reduction toggles from the actual value to the second. (e.g.

when actual state is normal it toggles to reduced). In case of power loss, the chip reverts to its prior state. At

activation of this feature the chip checks if sufficient power would be available, in case range reduction would be

active, to communicate with the tag. Only in case this condition is ensured the feature will be activated.

UCODE 9xm does not support the U bit and therefore ignores this value.

CommandRFU U

EPC

TID

User

Range

RN

CRC

No. of bits 16

2

1

6

2

1

2

16

16

Description 1110

0010

0000

0000

00

do

not

care

MSB:

"0": show memory above

EPC

"1": hide memory above

EPC

5 LSBs:

New EPC length

"00": hide none

"01": hide some

"10": hide all

"11": RFU

"0":

view

"1": hide

"00": normal

"01": toggle

"10":

reduced

"11": RFU

handle CRC-16

Table 11. Untraceable command

SL3S1005

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Product data sheet

Rev. 3.1 — 12 February 2025

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