LRIS64K datasheet(50/100 Pages) STMICROELECTRONICS

50 / 100 page

Explanation of the possible cases

LRIS64K

50/100

Doc ID 15336 Rev 11

Explanation of the possible cases

Figure 40 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.

●

LRIS64K_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 LRIS64Ks, LRIS64K_2 and LRIS64K_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 LRIS64K transmits a response. Therefore the VCD does not detect any

LRIS64K SOF and decides to switch to the next slot by sending an EOF.

●

In slot 3, there is another collision caused by responses from LRIS64K_4 and

LRIS64K_5

●

The VCD then decides to send a request (for instance a Read Block) to LRIS64K_1

whose UID has already been correctly received.

●

All LRIS64Ks detect an SOF and exit the anticollision sequence. They process this

request and since the request is addressed to LRIS64K_1, only LRIS64K_1 transmits a

response.

●

All LRIS64Ks 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 LRIS64K_1.

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