LRI1K datasheet(43/86 Pages) STMICROELECTRONICS

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LRI1K

Explanation of the possible cases

Doc ID 17170 Rev 3

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Explanation of the possible cases

Figure 39 summarizes the main possible cases that can occur during an anticollision

sequence when the slot number is 16.

The different steps are:

●

The VCD sends an Inventory request, in a frame terminated by an EOF. The number of

slots is 16.

●

LRI1K 1 transmits its response in Slot 0. It is the only one to do so, therefore no

collision occurs and its UID is received and registered by the VCD;

●

The VCD sends an EOF in order to switch to the next slot.

●

In slot 1, two LRI1Ks, LRI1K 2 and LRI1K 3 transmit a response, thus generating a

collision. The VCD records the event and remembers that a collision was detected in

Slot 1.

●

The VCD sends an EOF in order to switch to the next slot.

●

In Slot 2, no LRI1K transmits a response. Therefore the VCD does not detect any

LRI1K SOF and decides to switch to the next slot by sending an EOF.

●

In slot 3, there is another collision caused by responses from LRI1K 4 and LRI1K 5

●

The VCD then decides to send a request (for instance a Read Block) to LRI1K 1 whose

UID has already been correctly received.

●

All LRI1Ks detect an SOF and exit the anticollision sequence. They process this

request and since the request is addressed to LRI1K 1, only LRI1K 1 transmits a

response.

●

All LRI1Ks are ready to receive another request. If it is an Inventory command, the slot

numbering sequence restarts from 0.

Note:

The decision to interrupt the anticollision sequence is made by the VCD. It could have

continued to send EOFs until Slot 16 and only then sent the request to LRI1K 1.

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