T5557 Datasheet, PDF (8/30 Pages) ATMEL Corporation – Multifunctional 330-bit Read/Write RF-Identification IC

A start gap will be accepted at any time after the mode register has been loaded
(³ 3 ms). A single gap will not change the previously selected page (by former opcode
‘10’ or ‘11’).
Figure 9. Start of Reader to Tag Communication
Read mode
Write mode
d₁
d₀
Write Data Protocol
S gap
W gap
Table 2. Write Data Decoding Scheme
Parameters
Remark
Symbol Min.
Max.
Unit
Start gap
S_gap
10
50
FC
Write gap
Normal write mode
W_gap
8
30
FC
Write data in normal mode
‘0’ data
‘1’ data
d₀
16
31
FC
d₁
48
63
FC
The T5557 expects to receive a dual bit opcode as the first two bits of a reader com-
mand sequence. There are three valid opcodes:
• The opcodes ‘10’ and ‘11’ precede all block write and direct access operations for
page 0 and page 1
• The RESET opcode ‘00’ initiates a POR cycle
• The opcode ‘01’ precedes all test mode write operations. Any test mode access is
ignored after master key (bits 1..4) in block 0 has been set to ‘6’. Any further
modifications of the master key are prohibited by setting the lock bit of block 0 or the
OTP bit.
Writing has to follow these rules:
• Standard write needs the opcode, the lock bit, 32 data bits and the 3-bit address
(38 bits total)
• Protected write (PWD bit set) requires a valid 32-bit password between opcode and
data, address bits
• For the AOR wake-up command an opcode and a valid password are necessary to
select and activate a specific tag
Note: The data bits are read in the same order as written.
If the transmitted command sequence is invalid, the T5557 enters regular-read mode
with the previously selected page (by former opcode ‘10’ or ‘11’).
8 T5557
4517E–RFID–02/03