Nordic ID

Introduction

Protocol-control and extended protocol-control bitfields define some key characteristics of a tag. The information stored here includes tag EPC length and user memory characteristics.

Protocol-control (PC) word

PC is located in the second word of EPC memory. The difference between StoredPC and PackedPC is the implementation of L bits for EPC length. The tag can be instructed to reply with TID instead of EPC, and the tag modifies the L bits to match the length of TID.

StoredPC

StoredPC has the following information:

where

10          is the most significant bit.

1F          is the least significant bit.

L0 – L4 (EPC length field) indicates the length of EPC in 16 bit words (0 – 31 words).

RUM     (Read user memory indicator) indicates whether the tag has memory allocated to File_0 in the user memory bank. 

XI            (XPC_W1 indicator) indicates whether the tag has implemented XPC1 and that the XPC1 contains data.

T             (Numbering system identifier toggle) indicates whether the tag follows the GS1 EPCglobal Application standard (T=0) or the ISO/IEC 15961 standard (T=1). Note that this document covers only elements related to the GS1 standard.

RFU      Reserved for future use

PacketPC

PacketPC differs from StoredPC only by backscattering different EPC length (L0-L4 field) when commanded to return TID instead of EPC.
 

Extended protocol control (XPC) words

Extended protocol control words contain more information about the tag. XPC_W1 exists and contains a non-zero value if the XI bit in PC is 1. 

XPC_W2 exists and contains data if the XEB bit in XPC_W1 is 1.

XPC_W1

XPC word 1 contains the following data:

where

210       is the most significant bit.

21F       is the least significant bit.

XEB       (XPC_W2 indicator) XEB = 1 if XPC_W2 word exists and contains non-zero data.

RFU      Reserved for future use

SA          (Sensor Alarm indicator) has value 1 if the tag reports an alarm condition. If SA=0, the tag does not implement sensor alarm or the sensor alarm is not reported.

SS          (Simple Sensor indicator) is 1 if the tag has a simple sensor.

FS          (Full Function Sensor indicator) is 1 if the tag has a full function sensor.

SN         (Snapshot Sensor indicator) is 1 if the tag has a snapshot sensor.

B             (Battery-Assisted Passive indicator) is 1 if the tag is battery-assisted. B=0 if the tag doesn’t support the B flag or is passive.

C            (Computed Response indicator) is 1 if ResponseBuffer contains a response. C=0 if the tag doesn’t implement the C flag or ResponseBuffer is empty.

SLI         (SL indicator) is 1 if the tag has asserted the SL flag. SLI=0 if the tag has deasserted the SL flag or does not support SLI.

TN          (Notification indicator) is 1 if the tag asserts a notification. TN=0 if the tag does not assert a notification or does not support the TN flag.

U            (Untraceable indicator) is 1 if the tag is untraceable. U=0 if the tag is traceable or does not implement the U flag.

K             (Killable indicator) is 1 if the tag is killable. K=0 if the tag is not killable with the kill command or does not support the K flag.

NR         (Non-removable indicator) is 1 if the tag is non-removable from its host item. NR=0 if the tag is removable or does not support the NR flag.

H            (Hazmat indicator) is 1 if the tagged item is hazardous material. H=0 if the tagged item is not hazardous material or the tag does not support the H bit.

Note that the default setting for Nordic ID NurApi item 

public bool EnableXPCRemoval

is true. This means that both XPC_W1 and XPC_W2 are stripped from EPC and cannot be read. To read XPCs – if available – the value must be set to false with the command

hNur.XPCRemoval = false;

If XPC_W1 / XPC_W2 are available these will be added to the beginning of EPC. 

Example 1 (EnableXPCRemoval = false, XPC_W1 and XPC_W2 present):

Nordic ID RFID module responds with EPC = 81040C00E280B1202000000110024E7A

• XPC1_W1 = 0x8104
• XPC2_W1 = 0x0C00
• EPC = E280B1202000000110024E7A

Example 2 (EnableXPCRemoval = false, XPC_W1 present, XPC_W2 absent):

Nordic ID RFID module responds with EPC = 0104E280B1202000000110024E79             

• XPC_W1 = 0x0104
• EPC = E280B1202000000110024E79

Example 3 (EnableXPCRemoval = true, XPCs stripped away even if present):

Nordic ID RFID module responds with EPC = E280B1202000000110024E7A

IMPORTANT: If the XPC is present and it is not removed, any tag operations (read, write, lock, kill, etc.) that require the EPC will fail. 

XPC_W2

XPC_W2 can be used to get snapshot sensor values. There are three ways to initiate snapshot sensor measurements. A tag can support one or more methods.

1. Tag-initiated measurement triggered by tag power-up. The snapshot sensor information is available starting from the first inventory round that includes the Tag.
2. Reader-initiated measurement using the Select command to XPC2_W2. The snapshot sensor information is available starting from the next inventory round that includes the Tag if it remains energized. See |1| for details.
3. Reader-initiated measurement using the Write or BlockWrite command to XPC2_W2. The snapshot sensor information is available for a subsequent Read of XPC_W2 and/or starting from the next inventory round that includes the Tag. The reader can initiate a measurement regardless of the lock or permalock status of EPC memory. See |1| for details.

XPC_W2 bit assignments for methods 2 and 3:

The meaning of the values:

Sensor types and measurement units are defined here:

For detailed information about sensor data see table 8.1. and about data values table 8.2. in |1|.

References

|1| EPC® Radio-Frequency Identity Generation-2 UHF RFID Standard

https://ref.gs1.org/standards/gen2/

NurApi