FOR MOBILE APPLICATIONS
W25Q256FV
- 81 -
8.2.43
Read Security Registers (48h)
The Read Security Register instruction is similar to the Fast Read instruction and allows one or more data
bytes to be sequentially read from one of the four security registers. The instruction is initiated by driving
the /CS pin low and then shifting the instruction code “48h” followed by a 24/32-bit address (A23/A31-A0)
and eight “dummy” clocks into the DI pin. The code and address bits are latched on the rising edge of the
CLK pin. After the address is received, the data byte of the addressed memory location will be shifted out
on the DO pin at the falling edge of CLK with most significant bit (MSB) first. The byte address is
automatically incremented to the next byte address after each byte of data is shifted out. Once the byte
address reaches the last byte of the register (byte address FFh), it will reset to address 00h, the first byte
of the register, and continue to increment. The instruction is completed by driving /CS high. The Read
Security Register instruction sequence is shown in Figure 47. If a Read Security Register instruction is
issued while an Erase, Program or Write cycle is in process (BUSY=1) the instruction is ignored and will
not have any effects on the current cycle. The Read Security Register instruction allows clock rates from
D.C. to a maximum of F
R
(see AC Electrical Characteristics).
ADDRESS {A23/A31}-16
A15-12
A11-8 A7-0
Security Register #1
00h
0 0 0 1
0 0 0 0
Byte Address
Security Register #2
00h
0 0 1 0
0 0 0 0
Byte Address
Security Register #3
00h
0 0 1 1
0 0 0 0
Byte Address
/CS
CLK
DI
(IO
0
)
DO
(IO
1
)
Mode 0
Mode 3
0
1
2
3
4
5
6
7
Instruction (48h)
High Impedance
8
9
10
28
29
30
31
24-Bit Address
23
22
21
3
2
1
0
Data Out 1
*
/CS
CLK
DI
(IO
0
)
DO
(IO
1
)
32
33
34
35
36
37
38
39
Dummy Byte
High Impedance
40
41
42
44
45
46
47
48
49
50
51
52
53
54
55
7
6
5
4
3
2
1
0
7
Data Out 2
*
7
6
5
4
3
2
1
0
*
7
6
5
4
3
2
1
0
43
31
0
= MSB
*
Figure 47. Read Security Registers Instruction (SPI Mode only)
32-Bit Address is required when the device is operating in 4-Byte Address Mode
