T555401N-DDW Atmel, T555401N-DDW Datasheet - Page 13

• Manufacturer Part Number: T555401N-DDW
• Manufacturer: Atmel

Specifications of T555401N-DDW

• Screening Level: Industrial
• Lead Free Status / Rohs Status: Supplier Unconfirmed

4.11
4.12
4.13
4.14
4576D–RFID–12/06
Write
Start Gap
Decoder
Writing Data into the T5554
Writing data into the IC occurs via the Atmel write method. It is based on interrupting the RF field
with short gaps. The time between two gaps encodes the “0/1” information to be transmitted.
The first gap is the start gap which triggers write mode. In write mode, the damping is perma-
nently enabled which eases gap detection. The start gap may need to be longer than
subsequent gaps in order to be detected reliably.
A start gap will be detected at any time after block 0 has been read (field-on plus approximately
2 ms).
Figure 4-11. Start of Writing
The duration of the gaps is usually 50 to 150 µs. The time between two gaps is nominally 24 field
clocks for a “0” and 56 field clocks for a “1”. When there is no gap for more than 64 field clocks
after previous gap, the IDIC exits write mode; it starts with programming if the correct number of
valid bits were received.
If there is a gap fail - i.e., one or more of the intervals did represent not a valid “0” or “1” - the IC
does not program, but enters read mode beginning with block 1, bit 1.
The T5554 expects a 2-bit OP-code first. There are two valid OP-codes (“10” and “11”). If the
OP-code is invalid, the T5554 starts read mode beginning with block 1 after the last gap. The
OP-code (“10”) is followed by different information (see
Note:
• Standard writing needs the OP-code, the lock bit, the 32 data bits and the 3-bit block
• Writing with usePWD set requires a valid password between OP-code and address/data bits.
• In AOR mode with usePWD, OP-code and a valid password are necessary to enable
• The STOP OP-code is used to silence the T5554 (disable damping until power is cycled).
address.
modulation.
The data bits are read in the same order as written.
RF
Read mode
Start of writing
(start gap)
Write mode
Figure
4-11):
T5554
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