The hardware sector protection feature disables both
program and erase operations in any sector. The hardware
sector unprotection feature re-enables both program and
erase operations in previously protected sectors.
Sector protection/unprotection must be implemented using
programming equipment. The procedure requires a high
voltage (VID) on address pin A9 and the control pins.
The device is shipped with all sectors unprotected.
It is possible to determine whether a sector is protected or
unprotected. See "Autoselect Mode" for details.
Hardware Data Protection
The requirement of command unlocking sequence for
programming or erasing provides data protection against
inadvertent writes (refer to the Command Definitions table).
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 transitions, or from system noise. The device
is powered up to read array data to avoid accidentally writing
data to the array.
Write Pulse "Glitch" Protection
Noise pulses of less than 5ns (typical) on OE , CE or WE
do not initiate a write cycle.
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
reading array data on the initial power-up.
Temporary Sector Unprotect (N/A on A290021)
This feature allows temporary unprotection of previous
protected sectors to change data in-system. The Sector
Unprotect mode is activated by setting the RESET pin to
VID. During this mode, formerly protected sectors can be
programmed or erased by selecting the sector addresses.
Once VID is removed from the RESET pin, all the previously
protected sectors are protected again. Figure 1 shows the
algorithm, and the Temporary Sector Unprotect diagram
shows the timing waveforms, for this feature.
RESET = VID
Perform Erase or
RESET = VIH
Completed (Note 2)
1. All protected sectors unprotected.
2. All previously protected sectors are protected once again.
Figure 1. Temporary Sector Unprotect Operation
PRELIMINARY (June, 2000, Version 0.2)
AMIC Technology, Inc.