W25Q256FVBIF-TR Datasheet, PDF (79/108 Pages) Winbond – 3V 256M-BIT SERIAL FLASH MEMORY WITH DUAL/QUAD SPI & QPI

W25Q256FV
8.2.38 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 W25Q256FV 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 42.
/CS
CLK
Mode 3
Mode 0
DI
(IO₀)
DO
(IO₁)
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23
Instruction (4Bh)
Dummy Byte 1
Dummy Byte 2
High Impedance
/CS
CLK
DI
(IO₀)
DO
(IO₁)
23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42
Dummy Byte 3
Dummy Byte 4
* ^{= MSB}
High Impedance
63 62 61
210
* 64-bit Unique Serial Number
Mode 3
Mode 0
Figure 42. Read Unique ID Number Instruction (SPI Mode only)
5 Dummy Bytes are required when the device is operating in 4-Byte Address Mode
- 78 -
Publication Release Date: February 11, 2015
Preliminary – Revision H