There are several proprietary LF tags on the market. For these tags the ReadTag and WriteTag commands can be used. Here we describe the operation of standardized tags according ISO/IEC 18000-2. In addition, we describe simple tags with fixed codes or data that can be read only.
LF tags according ISO/IEC 18000-2 have no memory banks. The memory is organized block wise. A block is 32 bits. There may be up to 256 blocks. Maximum memory size is 1024 Bytes This is page 0. But additional memory may be added as pages 1…255.
Tag contain a system memory area with system information consisting of an optional Application Family Identifier (AFI, 1 byte), an optional Data storage format identifier (DSFID, 1 byte).
KillTag
There is no Kill command for LF tags.
LockTag
According ISO/IEC 18000-2 memory blocks can be locked, i.e. write operations to locked blocks are prohibited. Therefore, the State PermanentLock_2 is the only acceptable state. The mapping of the lock type is defined in Table B.1.
Table B.1 – LockType enumeration LF mapping
|
State |
Meaning |
|
Lock_0 |
not allowed |
|
Unlock_1 |
not allowed |
|
PermanentLock_2 |
Read operations to the memory area are allowed without limitation. Write operations to the memory area are not allowed under any circumstances. It is not possible to unlock the memory area again. |
|
PermanentUnlock_3 |
not allowed |
The mapping of the LockTag parameters is defined in Table B.2.
Table B.2 – LockTag LF parameter mapping
|
Command Argument |
Description |
|
Identifier |
AutoID Identifier according to the device configuration as returned as part of a ScanResult in a scan event or scan method. AFI and mask as part of the UII (0…48 bits) or no value, if no identifier is available. |
|
CodeType |
raw data |
|
Password |
no password defined |
|
Region |
to be set to 0 for memory, to be set to AFI for AFI, to be set to DSFID for DSFID |
|
Lock |
PermanentLock_2 |
|
Offset |
Start address of the memory area [byte counting]. It is up to the user to enter values as multiples of 4 or any other block length.To be set to 0 for AFI or DSFID. |
|
Length |
Length of the memory area [byte counting]. It is up to the user to enter values as multiples of 4 or any other block length.To be set to 1 for AFI or DSFID. |
|
Status |
Returns the result of the LOCK operation. The AutoIdOperationStatusEnumeration DataType is defined in 9.2.1. |
SetTagPassword
Commands for Change Password and Lock Password are listed in ISO/IEC 18000-2 but are not defined and reserved for future use.
As proprietary LF tags may use password commands this command should be defined here (for example transponder chip EM 4550). For EM 4550 the password is 4 bytes. Further parameters are Protection Word (4 bytes) and Control Word (4 bytes). Password mode must be set in order to read or write Protection Word or Control Word. Password is not used for other read or write operations.
The mapping of the SetTagPassword parameters is defined in Table B.3.
Table B.3 – SetTagPassword LF parameter mapping
|
Command Argument |
Description |
|
Identifier |
AutoID Identifier according to the device configuration as returned as part of a ScanResult in a scan event or scan method. AFI and mask as part of the UII or no value, if no identifier is available. |
|
CodeType |
raw data |
|
PasswordType |
|
|
AccessPassword |
not applicable |
|
NewPassword |
The new password of the tag, if unequal from zero (4 bytes, MSB first). |
|
Status |
Returns the result of the SetTagPassword method. |
ReadTag
Read and write operations according ISO/IEC 18000-2 are defined for blocks only. It is up to the user to use the correct values for Offset and Length. They must be multiples of 4.
There is a further read command “Get system information”. It reads the system memory block data, i.e. 104 bits = 13 bytes, including UII, AFI and DSFID (see ISO/IEC 18000-2 Table 25).
Region should be set to 0 for data. For UII/TID region should be set to 2. The region mapping is defined in Table B.4.
Table B.4 – ReadTag Region LF mapping
|
Region |
Meaning |
|
0 |
Read data area of the Tag |
|
1 |
not allowed |
|
2 |
TID bank, bank size is tag dependant |
|
3 |
not allowed |
|
4 |
Read AFI |
|
5 |
Read DSFID |
An access password is not defined for LF tags.
The mapping of the ReadTag parameters is defined in Table B.17.
Table B.5 – ReadTag LF parameter mapping
|
Command Argument |
Description |
|
Identifier |
AutoID Identifier according to the device configuration as returned as part of a ScanResult in a scan event or scan method. AFI and mask as part of the UII or no value, if no identifier is available. |
|
CodeType |
raw data |
|
Region |
To be set to 0 for memory, to be set to 2 for UII, to be set to 4 for AFI or to be set to 5 for DSFID |
|
Offset |
Start address of the memory area [byte counting]. It is up to the user to enter values as multiples of 4 or any other block length.To be set to 0 for AFI or DSFID. |
|
Length |
Length of the memory area [byte counting]. It is up to the user to enter values as multiples of 4 or any other block length.To be set to 1 for AFI or DSFID. |
|
Password |
no password |
|
ResultData |
Returns the requested tag data |
|
Status |
Returns the status of the read operation. |
ISO/IEC 18000-2 describes a system with read/write tags. In addition, there are many RFID systems on the market with read only transponders (ROM). Tags store only a fixed code that is factory programmed, or the user programs it himself (WORM). Such tags will be red with a read command. Region will be set to 0. Length will be set to 0 as well as the length of data cannot be changed.
WriteTag
Read and write operations according ISO/IEC 18000-2 are defined for blocks only. It is up to the user to use the correct values for Offset and Length. They must be multiples of 4.
There is a further write command “Write system data”. It writes the AFI (1 byte) or the DSFID (1 byte).
Region should be set to 0 for data. For UII/TID region should be set to 2. The region mapping is defined in Table B.6.
Table B.6 – WriteTag Region LF mapping
|
Region |
Meaning |
|
0 |
Write data area of the Tag |
|
1 |
not allowed |
|
2 |
TID bank, bank size is tag dependant |
|
3 |
not allowed |
|
4 |
Write AFI |
|
5 |
Write DSFID |
The length of the data is defined by the data itself.
The mapping of the WriteTag parameters is defined in Table B.7.
Table B.7 – WriteTag LF parameter mapping
|
Command Argument |
Description |
|
Identifier |
AutoID Identifier according to the device configuration as returned as part of a ScanResult in a scan event or scan method. AFI and mask as part of the UIIor no value, if no identifier available |
|
CodeType |
raw data |
|
Region |
to be set to 0 for memory, to be set to 4 for AFI, to be set to 5 for DSFID |
|
Offset |
Start address of the memory area [byte counting]. It is up to the user to enter values as multiples of 4 or any other block length.To be set to 0 for AFI or DSFID. |
|
Data |
Data to be written |
|
Password |
no password |
|
Status |
Returns the status of the read operation. |