In step 1, the interrogator (reader) issues a query. In step 2, the tag
responds with a randomly generated 16 bit number. The reader acknowledges by returning
a random 16 bit number in step 3. This selects only one tag with which to communicate. This
random number is designed to avoid contention between multiple tags and to ensure
that the reader is communicating with only a single tag. In step 4, only the tag that issued
the matching random number responds with its PC=EPC, essentially its identi?¬?er. In step 5,
the reader issues a transaction request with the same random number. The tag responds
with a transaction handle in step 6. In step 7, the actual transaction is issued with the handle
as a parameter. Finally, the tag responds to the transaction in step 8.
3.4.1 Speci?¬?cation of Macros
The communication transactions between the RFID reader and the tag can be broken down
into a series of RFID primitives. To automate the generation of the tag controller for the
prototype, these primitives are implemented as simple, assembly-like instructions called
RFID macros. For example, the RFID macros required for executing the Write command of
the ISO 18000 Part 6C standard are shown here. The format of the respective ?¬?elds
Convert to
RFID macros
RFID parser
rfpp
RFID compiler
rfcc
Embedded
C compiler
Microprocessorbased
RFID tag
Hardwarebased
RFID tag
Commercial
synthesis flow
C
VHDL
Include RFID
behavior
Behavior
template
RFID
specification
FIGURE 3.
Pages:
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118