M24LR04E-R datasheet(75/142 Pages) STMICROELECTRONICS

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M24LR04E-R

Explanation of the possible cases

Doc ID 022208 Rev 5

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Explanation of the possible cases

Figure 51 summarizes the main possible cases that can occur during an anticollision

sequence when the number of slots is 16.

The sequence of steps is as follows:

●

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

slots is 16.

●

M24LR04E-R_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 M24LR04E-Rs, M24LR04E-R_2 and M24LR04E-R_3 transmit a

response, thus generating a collision. The VCD records the event and registers 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 M24LR04E-R transmits a response. Therefore the VCD does not detect

any M24LR04E-R SOF and switches to the next slot by sending an EOF.

●

In Slot 3, another collision occurs due to responses from M24LR04E-R_4 and

M24LR04E-R_5.

●

The VCD sends a request (for instance a Read Block) to M24LR04E-R_1 whose UID

has already been correctly received.

●

All M24LR04E-Rs detect an SOF and exit the anticollision sequence. They process this

request and since the request is addressed to M24LR04E-R_1, only M24LR04E-R_1

transmits a response.

●

All M24LR04E-Rs 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 M24LR04E-R_1.

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