R
EM4223
Return link preamble
The FM0 return link preamble has the bit pattern described in Error! Reference source not found.
Tag bit periods
2
3
4
5
6
7
8
11 12
14
16
1
9
10
13
15
Preamble waveform
'1' is tag reflecting, '0' is tag not reflecting
Fig. 15 - FM0 Return link preamble
Cyclic Redundancy Check (CRC)
The 16 bit CRC is calculated on all data bits up to, but
not including, the first CRC bit.
The 16-bit register is preloaded with 'FFFF’. The resulting
CRC value is inverted, attached to the end of the packet
and transmitted.
The polynomial used to calculate the CRC is x^16 + x^12
+ x^5 + 1.
The most significant byte shall be transmitted first. The
most significant bit of each byte shall be transmitted first.
MSByte
LSByte
LSB
MSB
LSB
MSB
CRC 16 (8 bits)
↑ first transmitted bit of the CRC
CRC 16 (8 bits)
Fig. 16- CRC format
7. MEMORY ORGANISATION AND CONFIGURATION INFORMATION
Memory Map
Unambiguous User Data (UUD) & SUID
The physical memory comprises 128 bits of user
memory, 8 bits AFI and 3 personality bits. In addition, the
IC Manufacturer Code as specified in ISO7816-6/AM1 is
hard-wired into the Transponder.
The user memory on the Transponder comprises 128
bits of user specified data. This data is known as
Unambiguous User Data UUD, because it is expected
that this data be unique and unambiguous. The UUD is a
license plate defined by the user and may be an EPC™,
GTAG™ or other user defined number.
128 bits UUD memory
8 bit AFI
3 bits Personality
The Transponder will return a Sub-UID (SUID) as defined
in ISO 18000-6 when the SUID flag is =1 in the
arbitration initiation commands. The SUID in this
Transponder is derived from the least significant 32 bits
of the UUD as described below. The SUID consists of 40
bits: the 8 bit manufacturer code followed by the least
significant 32 bits of the UUD.
Fig. 17- Memory map
19
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