M24LR64-RMB6T2 datasheet(70/128 Pages) STMICROELECTRONICS

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Explanation of the possible cases

M24LR64-R

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Doc ID 15170 Rev 10

Explanation of the possible cases

Figure 51 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.

●

M24LR64-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 M24LR64-Rs, M24LR64-R_2 and M24LR64-R_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 M24LR64-R transmits a response. Therefore the VCD does not detect any

M24LR64-R SOF and decides to switch to the next slot by sending an EOF.

●

In slot 3, there is another collision caused by responses from M24LR64-R_4 and

M24LR64-R_5

●

The VCD then decides to send a request (for instance a Read Block) to M24LR64-R_1

whose UID has already been correctly received.

●

All M24LR64-Rs detect an SOF and exit the anticollision sequence. They process this

request and since the request is addressed to M24LR64-R_1, only M24LR64-R_1

transmits a response.

●

All M24LR64-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 M24LR64-R_1.

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