LRI512 View Datasheet(PDF) - STMicroelectronics
Part Name
Description
Manufacturer
LRI512
STMicroelectronics
LRI512 Datasheet PDF : 54 Pages
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LRI512
REQUEST PROCESSING BY THE LRI512
Upon reception of a valid Request, the LRI512
performs the following algorithm, where:
– NbS is the total number of slots (1 or 16)
– SN is the current slot number (0 to 15)
– LSB (value, n) function returns the n least signif-
icant bits of the value
– MSB (value, n) function returns the n most sig-
nificant bits of the value
– “&” is the concatenation operator
– Slot_Frame is either a SOF or an EOF
SN = 0
if (Nb_slots_flag)
then NbS = 1
SN_length = 0
endif
else NbS = 16
SN_length = 4
endif
label1:
if LSB(UID, SN_length + Mask_length) =
LSB(SN,SN_length)&LSB(Mask,Mask_length)
then answer to inventory request
endif
wait (Slot_Frame)
if Slot_Frame = SOF
then Stop Anticollision
decode/process request
exit
endif
if Slot_Frame = EOF
if SN < NbS-1
thenSN = SN + 1
goto label1
exit
endif
endif
EXPLANATION OF THE POSSIBLE CASES
Figure 32 summarizes the main possible cases
that can occur during an anti-collision 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.
– LRI512 #1 transmits its Response in Slot 0. It is
the only one to do so, therefore no collision oc-
curs and its UID is received and registered by
the VCD;
– The VCD sends an EOF, meaning to switch to
the next slot.
– In slot 1, two LRI512s, #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, meaning to switch to
the next slot.
– In Slot 2, no LRI512 transmits a Response.
Therefore the VCD does not detect a LRI512
SOF and decides to switch to the next slot by
sending an EOF.
– In slot 3, there is another collision caused by
Responses from LRI512 #4 and #5
– The VCD then decides to send a Request (for
instance a Read Block) to LRI512 #1, whose
UID was already correctly received.
– All LRI512s detect a SOF and exit the anti-colli-
sion sequence. They process this Request and
since the Request is addressed to LRI512 #1,
only LRI512 #1 transmits its Response.
– All LRI512s are ready to receive another Re-
quest. If it is an Inventory command, the slot
numbering sequence restarts from 0.
Note: the decision to interrupt the anti-collision se-
quence is up to the VCD. It could have continued
to send EOFs until Slot 15 and then send the Re-
quest to LRI512 #1.
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