NXP Commands
Readers which support NXP commands report the same in the field IsNXPCommandSupported of ReaderCaps as true. The following operations can be performed on NXPTags:
Set EAS – This feature can be used to set/reset the EAS (Electronic Article Surveillance) Bit. Tags can be monitored for EAS bit for the purpose of theft detection. For E.g. Tags with EAS enabled moving out could be an indication of unbilled item or theft. The methods SetEASWait and SetEASEvent allow setting or resetting the EAS bits on one or more NXP tags. An NXP tag with EAS bit set will raise an NXP_EAS_ALARM_EVENT when running EAS SCAN (NXP_EAS_SCAN) on the reader.
ReadProtect and ResetReadProtect- The feature to set ReadProtect sets the Quiet bit on one or more NXP tags. The methods for the same are ReadProtectEvent and ReadProtectWait. As a result, these tags trace-back a string of zeroes during Inventory and don't respond to access-operations, there by preventing unsecure access to Tag information. To put them back into normal mode, one has to call ResetReadProtectEvent.
Performing NXP Scan – To track NXP tags in which the EAS bit is set, an NXP_EAS_SCAN can be initiated on the reader by calling rfidApi.Actions.TagAccess.NXP.PerformEASScan or rfidApi.Actions.Inventory.Perform with its AntennaInfo parameter specifying NXP_EAS_SCAN as the OPERATION_QUALIFIER for atleast one of the Antenna IDs in the AntennaList array.
ushort[] antennaID = new ushort[rfidApi.ReaderCapabilities.NumAntennaSupported];
for (uint nIndex = 0; nIndex < antennaID.Length; nIndex++)
antennaID[nIndex] = (ushort)(nIndex + 1);
OPERATION_QUALIFER[] antennaOpList = new OPERATION_QUALIFER[rfidApi.ReaderCapabilities.NumAntennaSupported];
for (uint nIndex = 0; nIndex < antennaOpList.Length; nIndex++)
antennaOpList[nIndex] = OPERATION_QUALIFER.NXP_EAS_SCAN;
AntennaInfo antennaInfo = new AntennaInfo(antennaID, antennaOpList);
- Change Config - NXP G2iL and G2iL+ tags support a host of additional operations bank-wise read protection, product status flag, back scatter strength reduction. In addition G2iL+ tags offer more advanced features like read range reduction, tag tamper alarm, digital switch, data transfer mode, external power supply, external digital input. These additional features can be controlled (i.e. turned on/off) by modifying change Config word when the EPC of the tag is not locked. Config word is part of the tag’s EPC memory and setting/resetting the bits of the Config Word turns on/off the corresponding tag features.
NXP.ChangeConfigParams changeConfigParams = new NXP.ChangeConfigParams();
changeConfigParams.AccessPassword = 0x01;
changeConfigParams.NXPChangeConfigWord = 0x0002;
Given below is the list of the bits in Change Config word and the corresponding features it impacts.
| Bit Offset | Content | Remark |
|---|---|---|
| 0 | Tamper alarm flag ( G2iL+) | Indicator bit |
| 1 | External supply Input(G2iL+) | Indicator bit |
| 4 | Invert digital output | Temporary bit |
| 5 | Transparent mode on/off | Temporary bit |
| 6 | Transparent mode data/raw | Temporary bit |
| 9 | Maximum back scatter strength | Unlocked memory |
| 10 | Digital Output | Unlocked memory |
| 11 | Read range reduction on/off | Unlocked memory |
| 13 | Read protect EPC bank | Unlocked memory |
| 14 | Read protect TID bank | Unlocked memory |
Thus, a 16 bit Change Config word on a tag with unlocked EPC can turn on/off certain advanced features supported by G2iL tags and the tags reports back the modified Config word. However, setting the Change Config word to zero does not change the current Config word but the tag still responds with current Config word.