LRI64 datasheet(28/52 Pages) STMICROELECTRONICS

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Request processing by the LRI64

LRI64

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16.1

Explanation of the possible cases

Figure 21 summarizes the main possible cases that can occur during an anti-collision

sequence when the number of slots is 16.

The different steps are:

●

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

slots is 16.

●

LRI64 #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, to switch to the next slot.

●

In slot 1, two LRI64 devices, #2 and #3, transmit their Responses. This generates a

collision. The VCD records it, and remembers that a collision was detected in Slot 1.

●

The VCD sends an EOF, to switch to the next slot.

●

In Slot 2, no LRI64 transmits a Response. Therefore the VCD does not detect a LRI64

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

●

In slot 3, there is another collision caused by Responses from LRI64 #4 and #5

●

The VCD then decides to send a Request (for instance a Read Block) to LRI64 #1,

whose UID was already correctly received.

●

All LRI64 devices detect a SOF and exit the anti-collision sequence. They process this

Request and since the Request is addressed to LRI64 #1, only LRI64 #1 transmits its

Response.

●

All LRI64 devices 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 anti-collision sequence is up to the VCD. It could have

continued to send EOFs until Slot 15 and then send the Request to LRI64 #1.

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