AS3955 datasheet(33/102 Pages) AMSCO

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ams Datasheet

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[v1-04] 2016-Feb-03

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AS3955 − Detailed Description

Fabrication Data FAB_CFG3

Figure 32:

Fabrication Data FAB_CFG3

Note(s):

1. This byte can be set only during production.

Reserved Bytes

The reserved bytes belong to reserved memory areas.

OTP Blocks

Write and Read Lock blocks are OTP (One Time Programmable).

This means that once they are set to 1, they cannot be set back

to 0. Since setting OTP bits is an irreversible operation, it is

strongly recommended to perform this operation in controlled

environment.

Lock Bits

The bits of byte 2 and 3 of block 02h represent the

field-programmable read-only locking mechanism called

“static lock bytes”. They are called static because their position

in memory is fixed.

When data memory is larger than 16 blocks (64 bytes), also

“dynamic lock bytes” are required. They are located starting at

address 7Ah (4kbit version) and address 3Ah (2kbit version).

Block lock granularity is 1 block per bit for the first 16 blocks, 2

blocks per bit for the remaining blocks.

Lock bits are OTP, i.e. setting bits to 1b is an irreversible

operation. Bits at 0b can be set to 1b through a WRITE operation,

the result being a bit-wise OR with the current value.

Conf. Bit

Name

Default

Function

Note

uid_crc<7>

CRC value calculated on UID

uid_crc<6>

uid_crc<5>

uid_crc<4>

uid_crc<3>

uid_crc<2>

uid_crc<1>

uid_crc<0>

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