![](http://datasheet.mmic.net.cn/170000/S71PL191HB0BFI100_datasheet_9723326/S71PL191HB0BFI100_57.png)
May 7, 2004 S29PL127H_129H_00A1
S29PL127H/S29PL129H
41
Pre l i m i n a r y
To verify the protect/unprotect status of the SecSi Sector, follow the algo-
Once the SecSi Sector is locked and verified, the system must write the Exit SecSi
Sector Region command sequence to return to reading and writing the remainder
of the array.
The SecSi Sector lock must be used with caution since, once locked, there is no
procedure available for unlocking the SecSi Sector area and none of the bits in
the SecSi Sector memory space can be modified in any way.
SecSi Sector Protection Bits
The SecSi Sector Protection Bits prevent programming of the SecSi Sector mem-
ory area. Once set, the SecSi Sector memory area contents are non-modifiable.
Figure 4. SecSi Sector Protect Verify
Hardware Data Protection
The command sequence requirement of unlock cycles for programming or erasing
provides data protection against inadvertent writes. In addition, the following
hardware data protection measures prevent accidental erasure or programming,
which might otherwise be caused by spurious system level signals during VCC
power-up and power-down transitions, or from system noise.
Low VCC Write Inhibit
When VCC is less than VLKO, the device does not accept any write cycles. This pro-
tects data during VCC power-up and power-down. The command register and all
internal program/erase circuits are disabled, and the device resets to the read
mode. Subsequent writes are ignored until VCC is greater than VLKO. The system
must provide the proper signals to the control pins to prevent unintentional writes
when VCC is greater than VLKO.
Write 60h to
any address
Write 40h to SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
START
RESET# =
VIH or VID
Wait 1
s
Read from SecSi
Sector address
with A6 = 0,
A1 = 1, A0 = 0
If data = 00h,
SecSi Sector is
unprotected.
If data = 01h,
SecSi Sector is
protected.
Remove VIH or VID
from RESET#
Write reset
command
SecSi Sector
Protect Verify
complete