The Architecture of Electronic Data Carriers - RFID: Fundamentals and Applications in Contactless Smart Cards and Identification - page 272

Power
on

S 1

X 1

X 1

S 0

X 2 X 1

X 2

S 2

X 1

Figure 10.9 Example of a simple state diagram to describe a state machine

A switching network performs the required classification: If the state variable Z(t)
and the input variable are fed into its inputs, then the new state Z(t + 1 ) will occur at
the output (Figure 10.8). When the next timing signal is received this state is transferred
to the output of (transition triggered) flip-flops and thus becomes the new system state
S(t + 1 ) of the state machine.

10.1.3 Memory architecture

10.1.3.1 Read-only transponder

This type of transponder represents the low-end, low-cost segment of the range of RFID
data carriers. As soon as a read-only transponder enters the interrogation zone of a
reader it begins to continuously transmit its own identification number (Figure 10.10).
This identification number is normally a simple serial number of a few bytes with
a check digit attached. Normally, the chip manufacturer guarantees that each serial
number is only used once. More complex codes are also possible for special functions.
The transponder's unique identification number is incorporated into the transponder
during chip manufacture. The user cannot alter this serial number, nor any data on
the chip.
Communication with the reader is unidirectional, with the transponder sending its
identification number to the reader continuously. Data transmission from the reader
to the transponder is not possible. However, because of the simple layout of the data
carrier and reader, read-only transponders can be manufactured extremely cheaply.
Read-only transponders are used in price-sensitive applications that do not require
the option of storing data in the transponder. The classic fields of application are