
May 21, 2004 S29PL127_064_032J_00_A1
S29PL127J/S29PL064J/S29PL032J for MCP
57
Prelimin ary
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 Pulse “Glitch” Protection
Noise pulses of less than 3 ns (typical) on OE#, CE#, or WE# do not initiate a
write cycle.
Logical Inhibit
Write cycles are inhibited by holding any one of OE# = VIL, CE# = VIH or WE# =
VIH. To initiate a write cycle, CE# and WE# must be a logical zero while OE# is a
logical one.
Power-Up Write Inhibit
If WE# = CE# = VIL and OE# = VIH during power up, the device does not accept
commands on the rising edge of WE#. The internal state machine is automatically
reset to the read mode on power-up.
Figure 3. SecSi Sector Protect Verify
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