W25Q128BV
7.2.34 Read Unique ID Number (4Bh)
The Read Unique ID Number instruction accesses a factory-set read-only 64-bit number that is unique to
each W25Q128BV device. The ID number can be used in conjunction with user software methods to help
prevent copying or cloning of a system. The Read Unique ID instruction is initiated by driving the /CS pin
low and shifting the instruction code “4Bh” followed by a four bytes of dummy clocks. After which, the 64-
bit ID is shifted out on the falling edge of CLK as shown in Figure 32.
/CS
Mode 3
Mode 0
0
1
2
3
4
5
6
7
8
9
10 11 12 13 14 15 16 17 18 19 20 21 22 23
CLK
Instruction (4Bh)
Dummy Byte 1
Dummy Byte 2
DI
(IO0)
High Impedance
DO
(IO1)
/CS
23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Mode 3
Mode 0
CLK
Dummy Byte 3
Dummy Byte 4
DI
(IO0)
High Impedance
DO
(IO1)
63 62 61
2
1
0
= MSB
64-bit Unique Serial Number
*
*
Figure 32. Read Unique ID Number Instruction Sequence
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