ata556714n-ddt1 ATMEL Corporation, ata556714n-ddt1 Datasheet - Page 9

• Manufacturer Part Number: ata556714n-ddt1
• Description: Multifunctional 330-bit Read/write Rf Identification Ic
• Manufacturer: ATMEL Corporation

4.6
4.7
4874E–RFID–10/07
Reader to Tag Communication
Start Gap
Data is written to the tag by interrupting the RF field with short field gaps (on-off keying) in accor-
dance with the e5550 write method. The time between two gaps encodes the “0” or “1”
information to be transmitted (pulse interval encoding). The duration of the gaps is usually 50 µs
to 150 µs. The time between two gaps is nominally 24 field clocks for a “0” and 54 field clocks for
a “1”. When there is no gap for more than 64 field clocks after a previous gap, the ATA5567 exits
the write mode. The tag starts with the command execution if the correct number of bits were
received. If a failure is detected, the ATA5567 does not continue and will enter regular-read
mode.
The initial gap is referred to as the start gap. This triggers the reader to tag communication. Dur-
ing this mode of operation, the receive damping is permanently enabled to ease gap detection.
The start gap may need to be longer than subsequent gaps in order to be detected reliably.
A start gap will be accepted at any time after the mode register has been loaded ( 3 ms). A sin-
gle gap will not change the previously selected page (by former opcode “10” or “11”).
Figure 4-4.
Table 4-1.
Parameters
Start gap
Write gap
Write data in normal mode
Start of Reader to Tag Communication
Write Data Decoding Scheme
Normal write mode
Read mode
Remark
“0” data
“1” data
S
gap
Symbol
d
1
W
Write mode
S
d
d
gap
gap
0
1
d
n
W
gap
Min.
10
16
48
8
Max.
ATA5567
50
30
31
63
Unit
FC
FC
FC
FC
9