User's Manual Part 1

13,56 MHz Multitag Reader Module, Version 0.9v
ACG Identification Technologies AT Page 13
3.8.3 Lock bytes
On page 2 the lock bytes are stored. Each bit specifies a page or block. Once a bit is
set it cannot be changed anymore. This process is irreversible. If a block lock bit is
set all pages within this block are read only regardless the single lock states. This
register is implemented as OTP
Byte 1 Byte 0
MSB LSB MSB LSB
7 6 5 4 3 2 1 0 7 6 5 4 3 2 1 0
Page F
Page E
Page D Page C
Page B Page A
Page 9 Page 8 Page 7 Page 6 Page 5 Page 4
OTP
Block A-F
Block 4-9
OTP
Figure 3-15: Lock bytes of Mifare® Ultralight
3.8.4 OTP bytes
Page 3 is implemented as OTP register. All bits are factory programmed to 0. Once a
bit is set it cannot be changed furthermore. It can be used as a 32 bit one-time
counter.
3.8.5 User data
User data is free for use. It can be changed according the write access condition.