ATA559001-6DSY Atmel, ATA559001-6DSY Datasheet - Page 79

• Manufacturer Part Number: ATA559001-6DSY
• Description: RF Wireless Misc UHF (1k bit r/w anti-collision)
• Manufacturer: Atmel

Specifications of ATA559001-6DSY

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

12. Aloha-based Anticollision Procedure
4817C–RFID–03/07
Aloha anticollision is based on a slot mechanism. A tag calculates a slot number by a random
counter.
Inside each slot, a tag can communicate with the reader if the calculated slot value is the same
as the slot number which is under control of the reader.
ATA5590 generates a slot number between 1 and 31. The first slot is used by each tag. If only
one tag is there, the reader has the full access to it during this first slot.
Therefore, the Aloha system is based on 32 slots. The maximum number of slots is fixed.
The Aloha procedure starts with
Therefore, the reader is able to control the participants by group or deterministic anticollision
commands. If ID_s was set before, the tag is silent.
After receiving a slot command, the tag backscatters the 16-bit random value, and the contents
of the ID page (128 bits) back to the reader. The same ID information is backscattered if the slot
number is the same as the slot number given by the reader, and the tag was selected before.
The slot counter is incremented by each of the above mentioned slot commands. If the reader
wants to have a message repeated, it can transmit the slot_repeat command. The Aloha proce-
dure is closed by the slot_close command. If the reader has detected a collision (for example,
during the random value, if the ID was not unique), the reader can skip the slot by sending the
command skip_slot.
The reader is also able to use all the other commands during Aloha, including deterministic anti-
collision and group-selection commands. Therefore, the Aloha procedure which is implemented
in ATA5590 does not need an adaptive round mechanism.
The status2 register which is backscattered after long commands also contains the Aloha infor-
mation (status2(2)).
If the communication was started in Aloha mode, the tag enters the isolated state (ID_s is set)
when:
ID_s can be reset by the reset command.
If the reader transmits deterministic anticollision commands during an active slot, the ID and the
ID_s flags work as described in
• Slot, or
• Slot_selected, or
• Slot_not_selected
• The slot number is equal to the internal slot number (on-chip), and
• When it receives a slot command
Figure 12-1 on page
80.
ATA5590
79