AM29F004B AMD [Advanced Micro Devices], AM29F004B Datasheet - Page 14

• Manufacturer Part Number: AM29F004B
• Description: 4 Megabit (512 K x 8-Bit) CMOS 5.0 Volt-only Boot Sector Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

Temporary Sector Unprotect
This feature allows temporary unprotection of previously pro-
tected sectors to change data in-system. The Sector
Unprotect mode is activated by setting the OE# pin to 12.0
Volts (V
page 28
grams, for this feature. While OE# is at V
sequence is written to the device. After the sector unlock
sequence is written, the OE# pin is taken back to V
device is now in the temporary sector unprotect mode.
While in this mode, formerly protected sectors can be pro-
grammed or erased by selecting the appropriate sector
address during programming or erase operations. Either
sector erase or chip erase operations can be performed in
this mode. Byte program operations require only two cycles,
while sector and chip erase operations only require four
cycles. Refer to the Command Definitions table.
Exiting the temporary sector unprotect mode is accomplished
by either removing V
back to V
After writing the sector relock sequence, the OE# pin is taken
back to V
again.
12
ID
IH
ID
and
).
and all previously protected sectors are protected
Figure 2
and writing the sector relock sequence.
Figure 17, on page 28
shows the algorithm, and
CC
from the device or by taking OE#
A D V A N C E
show the timing dia-
ID
, the sector unlock
Figure 16, on
IH
. The
Am29F004B
I N F O R M A T I O N
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once again.
Figure 2. Temporary Sector Unprotect Operation
Sector Relock sequence (Fig-
Unlock sequence with com-
mand 20h (Figure 16)
Write the three-cycle
Program Operations
Completed (Note 2)
OE# = V
Write the two-cycle
Temporary Sector
Perform Erase or
OE# = V
OE# = V
OE# = V
Unprotect
START
ure 17)
IH
(Note 1)
ID
ID
IH
8/5/05