mx25l3255d Macronix International Co., mx25l3255d Datasheet - Page 25

• Manufacturer Part Number: mx25l3255d
• Description: Security Serial Flash
• Manufacturer: Macronix International Co.

Table 6. Security Register Definition
P/N: PM1431
The sequence of issuing RDSCUR instruction is : CS# goes low→ send ing RDSCUR instruction → Security Regis-
ter data out on SO→ CS# goes high.
The definition of the Security Register bits is as below:
Secured OTP Indicator bit. The Secured OTP indicator bit shows the chip is locked by factory before ex- factory or
not. When it is "0", it indicates non- factory lock; "1" indicates factory- lock.
Lock-down Secured OTP (LDSO) bit. By writing WRSCUR instruction, the LDSO bit may be set to "1" for cus-
tomer lock-down purpose. However, once the bit is set to "1" (lock-down), the LDSO bit and the 4K-bit Secured OTP
area cannot be update any more. While it is in 4K-bit secured OTP mode, array access is not allowed.
Continuously Program Mode (CP mode) bit. The Continuously Program Mode bit indicates the status of CP
mode, "0" indicates not in CP mode; "1" indicates in CP mode.
(24) Write Security Register (WRSCUR)
The WRSCUR instruction is for changing the values of Security Register Bits. The WREN instruction is not required
before sending WRSCUR instruction. The WRSCUR instruction may change the values of bit1 (LDSO bit) for
customer to lock-down the 4K-bit Secured OTP area. Once the LDSO bit is set to "1", the Secured OTP area cannot
be updated any more.
The sequence of issuing WRSCUR instruction is :CS# goes low→ sending WRSCUR instruction → CS# goes high.
The CS# must go high exactly at the boundary; otherwise, the instruction will be rejected and not executed.
volatile bit
reserved
bit7
x
volatile bit
reserved
bit6
x
volatile bit
reserved
bit5
x
Program mode
Program mode
Continuously
1=CP mode
(CP mode)
(default=0)
volatile bit
0=normal
bit4
volatile bit
25
reserved
bit3
x
volatile bit
reserved
bit2
x
MX25L3255D
program/erase
non-volatile bit non-volatile bit
1 = lock-down
0 = not lock-
(indicate if
lock-down
(cannot
LDSO
down
OTP)
bit1
REV. 0.03, MAR. 13, 2009
0 = non-factory
Secrured OTP
indicator bit
1 = factory
bit0
lock
lock