7 us;
if Lprev????™1??™ then Sig????™0??™ after 0 ns & ??™1??™ after 0.7 us;
T??1.5 us; A??15%;
??™1??™: if Lprev????™0??™ then Sig????™1??™ after 0 us;
if Lprev????™1??™ then Sig????™0??™ after 0 us;
T??6.2 us; A??7%;
if Lprev????™0??™ then Sig????™1??™ after 0 us;
if Lprev????™1??™ then Sig????™0??™ after 0 us;
T??3.9 us; A??10%;
if Lprev????™0??™ then Sig????™1??™ after 0 us;
if Lprev????™1??™ then Sig????™0??™ after 0 us;
T??3.1 us; A??10%;
if Lprev????™0??™ then Sig????™1??™ after 0 us;
if Lprev????™1??™ then Sig????™0??™ after 0 us;
T??1.5 us; A??15%;
FIGURE 3.9
Textual description of FM0 encoding.
42 RFID Handbook: Applications, Technology, Security, and Privacy
commence. Figure 3.12 shows an example preamble using a textual preamble description
starting with a 15 ms pulse followed by 5 ms pulses separated by 10 ms. A typical preamble
could continue for several more pulses.
RFID standards may also specify transmission protocols between readers and tags. Thus,
corresponding transmission characteristics must be declared. For example, the transmission
protocol de?¬?ned in ISO 18000 Part 7 speci?¬?es that an RFID reader transmits the least
signi?¬?cant bit (LSb) ?¬?rst within a byte and sends the most signi?¬?cant byte (MSB) ?¬?rst
within a packet. Each byte is followed by a stop bit within a packet. The transmission order
determines the sequence of the serial-to-parallel process for receiving, and the parallel-toserial
sequence for responding.
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