Essel Technology RFID A1, User Manual, Page: 20 / 60

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3.3.11 Authentication Key / Password Register
Table 3.9
The Authentication Key and Password Registers are forty 6-bytes long registers, located at address 0x0168 to 0x0257,
with both read and write access but only after first unlocking the device. These registers are inaccessible when the
module is locked. When working with Mifare Classic tags these registers contain the password keys used for block
authentication in the tag. When working with Ultralight and NTAG transponders, these registers contain 4-byte
passwords. There are forty Authentication Key and Password registers numbered from 0 to 39. The number of the
key register to be used is passed as an argument in some commands.
3.3.12 User Memory
There are 128 bytes of memory available for the user as a protected memory space from address 0x0258 to 0x02D7.
This memory is inaccessible when the device is locked. This data is stored into non-volatile memory when the Lock
command is executed.
Register Name
Register Address
Byte Offset 0x00 0x01 0x02 0x03 0x04 0x05
Byte Position
0 1 2 3 4 5
Access
R/W R/W R/W R/W R/W R/W
Factory Default Value 0x00 0x00 0x00 0x00 0x00 0x00
Read Function
KEY[0] /
PASS[0]
KEY[1] /
PASS[1]
KEY[2] /
PASS[2]
KEY[3] /
PASS[3]
KEY[4] KEY[5]
Write Function
KEY[0] /
PASS[0]
KEY[1] /
PASS[1]
KEY[2] /
PASS[2]
KEY[3] /
PASS[3]
KEY[4] KEY[5]
0x0168, 0x016E … 0x0252
Authentication Key / Password