MB89R119B datasheet(20/46 Pages) RAMXEED

20 / 46 page

MB89R119B

DS411-00002-4v0-E

11. Anti-Collision Sequence



Execution of anti-collision sequence

The following steps summarize the main cases that can occur during a typical anti-collision sequence where

the number of slots is 16.

(1) The reader/writer sends an Inventory command. The Nb_slots_flag of the request flags is set to “0” to

specify the number of slots.

(2) In slot 0, transponder 1 transmits its response in the time t1_a from the detection of the rising edge of the

EOF. In this case no collision occurs and the UID of transponder is received and registered by the reader/

writer.

(3) The reader/writer sends an EOF signal to switch to the next slot in the time t2_a after the response 1.

(4) In slot 1, transponder 2 and transponder 3 transmit its response in the time t1_a from the detection of the

rising edge of the EOF. In this case, the reader/writer cannot recognize the UIDs of the two transponders

because the collision occurs, and the reader/writer remembers that a collision was detected in slot 1.

(5) The reader/writer sends an EOF signal to switch to the next slot in the time t2_a after the responses.

(6) In slot 2, no transponder transmits a response. The reader/writer does not detect any response, and

sends an EOF signal to switch to the next slot in the time t3_a from the detection of the rising edge of

the EOF.

(7) In slot 3, transponder 4 and transponder 5 transmit its response in the time t1_a from the detection of the

rising edge of the EOF, and another collision occurs.

(8) The reader/writer sends a request (for example, a Read Single Block command, described later) to the

transponder 1, which UID was already correctly received.

(9) All transponders detect an SOF signal and exit the anti-collision sequence. In this case, since the request

is addressed to transponder 1 (Address Mode), only transponder 1 transmits its response.

(10)All transponders are ready to receive another request from the reader/writer. If the Inventory command is

sent again, the anti-collision sequence starts from slot 0.

Note: t1_a, t2_a, t3_a are specified in clause 12.

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