ST25TB02K datasheet(20/47 Pages) STMICROELECTRONICS

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Table 8. Standard anticollision sequence

Step 1

Init:

Send Initiate().

•

If no answer is detected, go to step1.

•

If only 1 answer is detected, select and access the ST25TB02K. After accessing the ST25TB02K,

deselect the tag and go to step1.

•

If a collision (many answers) is detected, go to step2.

Step 2

Slot 0

Send Pcall16().

•

If no answer or collision is detected, go to step3.

•

If 1 answer is detected, store the Chip_ID, Send Select() and go to step3.

Step 3

Slot 1

Send Slot_marker(1).

•

If no answer or collision is detected, go to step4.

•

If 1 answer is detected, store the Chip_ID, Send Select() and go to step4.

Step 4

Slot 2

Send Slot_marker(2).

•

If no answer or collision is detected, go to step5.

•

If 1 answer is detected, store the Chip_ID, Send Select() and go to step5.

Step N

Slop N

Send Slot_marker(3 up to 14) ...

•

If no answer or collision is detected, go to stepN+1.

•

If 1 answer is detected, store the Chip_ID, Send Select() and go to stepN+1.

Step 17 Slot 15

Send Slot_marker(15).

•

If no answer or collision is detected, go to step18.

•

If 1 answer is detected, store the Chip_ID, Send Select() and go to step18.

Step 18 -

All the slots have been generated and the Chip_ID values should be stored into the reader memory. Issue

the Select(Chip_ID) command and access each identified ST25TB02K one by one. After accessing each

ST25TB02K, switch them into Deselected or Deactivated state, depending on the application needs.

•

If collisions were detected between Step2 and Step17, go to Step2.

•

If no collision was detected between Step2 and Step17, go to Step1.

After each Slot_marker() command, there may be no answer, one or several answers from the ST25TB02K

devices. The reader must handle all the cases and store all the Chip_IDs, correctly decoded. At the end of the

anticollision sequence, after Slot_marker(15), the reader can start working with one ST25TB02K by issuing a

Select() command containing the desired Chip_ID. If a collision is detected, the reader has to generate a new

sequence in order to identify all unidentified ST25TB02K devices in the field. The anticollision sequence can stop

when all ST25TB02K devices have been identified.

Table 9 gives an example of anticollision sequence, the cells containing (*) highlight the fact that the related tags

are not yet identified. When the tag is identified, in the table the (*) changes to bold character.

Table 9. Example of an anticollision sequence

Command

Tag1

Tag2

Tag3

Tag4

Tag5

Tag6

Tag7

Tag8

Comment

Chip_ID Chip_ID Chip_ID Chip_ID Chip_ID Chip_ID Chip_ID Chip_ID

READY state

28h(*)

75h(*)

40h(*)

01h(*)

02h(*)

FEh(*)

A9h(*)

7Ch(*)

Each tag gets a random Chip_ID

INITIATE()

40h(*)

13h(*)

3Fh(*)

4Ah(*)

50h(*)

48h(*)

52h(*)

7Ch(*)

Each tag get a new random Chip_ID.

All tags answer: collisions

PCALL16()

45h(*)

12h(*)

30h(*)

43h(*)

55h(*)

43h(*)

53h(*)

73h(*)

All CHIP_SLOT_ NUMBERs get a

new random value

SELECT(30h)

(*)

(*)30h

(*)

Slot0: only one answer

SLOT_MARKER(1) (*)

(*)

30h

(*)

(*)-

(*)

Slot1: no answer

SLOT_MARKER(2) (*)

12h(*)

(*)

Slot2: only one answer

SELECT(12h)

(*)

12h

(*)

Tag2 is identified

SLOT_MARKER(3) (*)

43h(*)

(*)

43h(*)

53h(*)

73h(*)

Slot3: collision

SLOT_MARKER(4) (*)

(*)

Slot4: no answer

ST25TB02K

Description of an anticollision sequence

DS11469 - Rev 7

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