ATA555811C-DDB Atmel, ATA555811C-DDB Datasheet - Page 21

• Manufacturer Part Number: ATA555811C-DDB
• Description: IC IDIC 1KBIT R/W DIE
• Manufacturer: Atmel

Specifications of ATA555811C-DDB

• Function: Read/Write
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4681E–RFID–11/09
b) The interrogator can detect whether any tag is present.
c) The interrogator checks the tag responses bit-wise within the anticollision loop.
d) The interrogator checks and eliminates tags.
e) End of a single anticollision loop
f) The interrogator communicates directly with tag in Selected state.
If no SOF pattern is returned then there is no tag present within the detection group so the
process continues with (a).
If one or more active tags are within range, the interrogator will sequentially scan the Tag ID
bits from the most significant through to the least significant bits. Each time slot corresponds
to a particular Tag ID bit position. All tags reply simultaneously with dual pattern modulated
data, the response signals being superimposed on one another. A damped signal will thus
overwrite a non-damped signal so that a logical 1 Tag ID bit will prevail over a logical 0 bit.
If the interrogator detects a Tag ID logical 1 bit, it acknowledges reception by broadcasting a
gap in the field signal. This can be monitored and evaluated by all tags within the detection
group. Otherwise a Tag ID logical 0 bit induces no reaction from the interrogator.
On observing an acknowledge gap, any individual tag can, by checking the state of it’s own
current Tag ID bit, deduce whether it should remain in the current anticollision detection loop
(Tag ID bit = 1) or whether it should eliminate itself from the detection group (Tag ID bit = 0).
Eliminated tags will be muted and fall back into the READY state where they take no further
part in the current detection loop. They remain in this state until the next anticollision loop is
started by a new GetID command. Continue to (a)
Non eliminated tags remain in the detection loop and if the final Tag ID bit has not been
reached then the next Tag ID bit is interrogated in (c) otherwise (e).
By the time the final Tag ID bit has been interrogated, there will be only one remaining active
tag within range – all others having been eliminated during the previous interactions.
Assuming no new tags have entered the interrogation since the start of the anticollision loop
and that all the signals have been correctly interpreted, the interrogator should at this stage
be able to identify the associated Tag ID. This active tag is set automatically into the
Selected state and replies with the anticollision response which consists of an SOF followed
a 16 bit CRC generated from it’s own Tag ID. If the received CRC matches the Tag ID the
interrogator may continue with (a) or (f).
If the received CRC is corrupted or does not match the calculated 16 bit value the interroga-
tor will issue a ResetSelected command to transfer this improperly selected tag back into the
READY state. Continue to (a).
At this stage the single identified and selected tag can undergo direct communication with
the interrogator and can be read and written with either Read, Write or Login commands.
This tag remains selected until the interrogator starts a new anticollision loop with a new
GetID command, or if other tags are addressed directly using a Select or GroupSelect com-
mand. The selected tag then drops into the Quiet state where it is excluded from all future
anticollision detection loops. Continue to (a).
ATA5558
21