ATA555811-DDT ATMEL [ATMEL Corporation], ATA555811-DDT Datasheet - Page 11

• Manufacturer Part Number: ATA555811-DDT
• Description: 1 kbit R/W IDIC with Deterministic Anticollision
• Manufacturer: ATMEL [ATMEL Corporation]

3.1.2
3.2
4681C–RFID–09/05
Interrogator to Tag Communication
Public Mode
Figure 3-2.
All commands and data bit streams from the interrogator to the tag are 100% (OOK –
On-Off-Key) modulated using a modified 1 out of 4 pulse position coding. Depending on the
data, the continuous RF field is interspersed with short field gaps of constant duration and vari-
able separation. The time from one gap to the next may take on one of four discrete values.
Each of these represent one of four possible dual bit downlink data codes ( 00 .. 11 ) in the data
stream (see
rate (DDR) bit set in the tag configuration block, so that selected tags can always understand the
interrogator. The minimum write data coding (maximum data rate) is 9 field clocks. This corre-
sponds with the d
Figure 3-3.
1. In Public Mode the cyclic data stream will be preceded by a single SOF pattern after the
2. The variable number of preamble data bits is aimed at easing the interrogator design
3. Within any closed identification system the preamble length for all tags must be
completion of the POR delay.
and optimizing system performance.
identical.
Figure
SOF Pattern
Interrogator to Tag - Modified 1 out of 4 Pulse Position Coding
Uplink mode
00
(d
3-3). The downlink data transfer speed is dependent on the downlink data
ref
) parameter in
S
gap
Preamble length = 3
p = 4 bit periods
Example with
d
ref
Figure 3-3
d
01
Downlink mode
SOF
W
and
gap
ATA5558 [Preliminary]
Table 3-1 on page
d
11
2 bit period
violation
code
d
10
d
12.
00
11