SRI4K-A3T/1GE STMicroelectronics, SRI4K-A3T/1GE Datasheet - Page 16

• Manufacturer Part Number: SRI4K-A3T/1GE
• Manufacturer: STMicroelectronics

Specifications of SRI4K-A3T/1GE

• Operating Temperature (max): 85C
• Operating Temperature Classification: Commercial
• Lead Free Status / Rohs Status: Compliant

SRI4K
ANTI-COLLISION
The SRI4K provides an anti-collision mechanism
that searches for the Chip_ID of each device that
is present in the reader field range. When known,
the Chip_ID is used to select an SRI4K individual-
ly, and access its memory. The anti-collision se-
quence is managed by the reader through a set of
commands described in the
section:
The reader is the master of the communication
with one or more SRI4K device(s). It initiates the
tag communication activity by issuing an INI-
TIATE(), PCALL16() or SLOT_MARKER() com-
mand to prompt the SRI4K to answer. During the
anti-collision sequence, it might happen that two or
more SRI4K devices respond simultaneously, so
causing a collision. The command set allows the
reader to handle the sequence, to separate SRI4K
transmissions into different time slots. Once the
anti-collision sequence has completed, SRI4K
communication is fully under the control of the
reader, allowing only one SRI4K to transmit at a
time.
The Anti-collision scheme is based on the defini-
tion of time slots during which the SRI4K devices
Figure 22. SRI4K Chip_ID Description
Each time the SRI4K receives a PCALL16() com-
mand, the CHIP_SLOT_NUMBER is given a new
4-bit random value. If the new value is 0000
SRI4K returns its whole 8-bit Chip_ID in its answer
to the PCALL16() command. The PCALL16() com-
mand is also used to define the slot number 0 of
the anti-collision sequence. When the SRI4K re-
ceives the SLOT_MARKER(SN) command, it
16/41
INITIATE()
PCALL16()
SLOT_MARKER().
b7
b6
“SRI4K
b5
OPERATION”
b4
b
, the
8-bit Chip_ID
are invited to answer with minimum identification
data: the Chip_ID. The number of slots is fixed at
16 for the PCALL16() command. For the INI-
TIATE() command, there is no slot and the SRI4K
answers after the command is issued. SRI4K de-
vices are allowed to answer only once during the
anticollision sequence. Consequently, even if
there are several SRI4K devices present in the
reader field, there will probably be a slot in which
only one SRI4K answers, allowing the reader to
capture its Chip_ID. Using the Chip_ID, the reader
can then establish a communication channel with
the identified SRI4K. The purpose of the anti-colli-
sion sequence is to allow the reader to select one
SRI4K at a time.
The SRI4K is given an 8-bit Chip_ID value used by
the reader to select only one among up to 256 tags
present within its field range. The Chip_ID is initial-
ized with a random value during the READY state,
or after an INITIATE() command in the INVENTO-
RY state.
The four least significant bits (
Chip_ID
CHIP_SLOT_NUMBER. This 4-bit value is used
by the PCALL16() and SLOT_MARKER() com-
mands during the anti-collision sequence in the IN-
VENTORY state.
compares its CHIP_SLOT_NUMBER with the
SLOT_NUMBER parameter (SN). If they match,
the SRI4K returns its Chip_ID as a response to the
command. If they do not, the SRI4K does not an-
swer. The SLOT_MARKER(SN) command is used
to define all the anti-collision slot numbers from 1
to 15.
b3
b0 to b3: CHIP_SLOT_NUMBER
b2
are
also
b1
known
b
0
b0
to b
as
3
) of the
ai07668
the