Performance is rarely an issue
because of the limited transmission speeds of the RF protocols.
if (current_state !?? KILLED) {
if (((current_state ?? ?? ACKNOWLEDGED) jj (current_state ?? ?? OPEN)
jj (current_state ?? ?? SECURED)) && ((sel_var ?? ?? sel)
&& (target_var ?? ?? target))) {
if (session ?? ?? last_session) {
if (inventoryFlag ?? ?? ??™A??™)
inventoryFlag????™B??™;
else if (inventoryFlag ?? ?? ??™B??™)
inventoryFlag????™A??™ ;
} else {
slot_counter??rand ((1 << Q)1) ;
if (slot_counter !?? 0)
current_state??ARBITRATE;
else
current_state??REPLY;
if (current_state ?? ?? REPLY)
RN16??slot_counter;
}
}
}
FIGURE 3.24
Tag behavior for Query command.
52 RFID Handbook: Applications, Technology, Security, and Privacy
For RFID tags, area is the primary concern as the size of the circuit results in a direct per
part cost impact. In many cases, the memory components of the controllers dominate the
area impact. In some cases this is dominated by the ?¬?rmware for a microprocessor-based
solution and in others by the memory used for storage in memory-enabled RFID tags.
Power optimization is important in RFID systems as the power supplied to the tags is
?¬?xed and battery drain needs to be limited. Because active systems are designed for
extremely low-cost large-scale applications, frequent replacement of batteries is not feasible.
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