AM29F200 AMD [Advanced Micro Devices], AM29F200 Datasheet - Page 11

• Manufacturer Part Number: AM29F200
• Description: 2 Megabit (256 K x 8-Bit/128 K x 16-Bit) CMOS 5.0 Volt-only, Boot Sector Flash Memory
• Manufacturer: AMD [Advanced Micro Devices]

L = Logic Low = V
Sector Protection/Unprotection
The hardware sector protection feature disables both
program and erase operations in any sector. The hard-
ware 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 (V
control pins. Details on this method are provided in a
supplement, publication number 20551. Contact an
AMD representative to obtain a copy of the appropriate
document.
The device is shipped with all sectors unprotected.
AMD offers the option of programming and protecting
sectors at its factory prior to shipping the device
through AMD’s ExpressFlash™ Service. Contact an
AMD representative for details.
It is possible to determine whether a sector is protected
or unprotected. See “Autoselect Mode” for details.
Temporary Sector Unprotect
This feature allows temporary unprotection of previ-
ously protected sectors to change data in-system. The
Sector Unprotect mode is activated by setting the
RESET# pin to V
tected sectors can be programmed or erased by
selecting the sector addresses. Once V
from the RESET# pin, all the previously protected
sectors are protected again. Figure 1 shows the algo-
rithm, and the Temporary Sector Unprotect diagram
(Figure 18) shows the timing waveforms, for this
feature.
Manufacturer ID: AMD
Device ID:
Am29F200B
(Top Boot Block)
Device ID:
Am29F200B
(Bottom Boot Block)
Sector Protection Verification
Description
IL
, H = Logic High = V
ID
. During this mode, formerly pro-
Mode
Word
Word
Byte
Byte
Table 4. Am29F200B Autoselect Codes (High Voltage Method)
ID
) on address pin A9 and the
CE#
L
L
L
L
L
L
OE#
IH
L
L
L
L
L
L
, SA = Sector Address, X = Don’t care.
ID
WE#
H
H
H
H
H
H
is removed
A16
A12
SA
to
X
X
X
Am29F200B
A11
A10
to
X
X
X
X
V
V
V
V
A9
Hardware Data Protection
The command sequence requirement of unlock cycles
for programming or erasing provides data protection
against inadvertent writes (refer to the Command Defi-
nitions table). In addition, the following hardware data
protection measures prevent accidental erasure or pro-
Notes:
1. All protected sectors unprotected.
2. All previously protected sectors are protected once
Figure 1. Temporary Sector Unprotect Operation
ID
ID
ID
ID
again.
A8
A7
to
X
X
X
X
A6
L
L
L
L
A5
A2
to
X
X
X
X
Program Operations
Completed (Note 2)
Temporary Sector
Perform Erase or
A1
H
L
L
L
RESET# = V
RESET# = V
Unprotect
(Note 1)
START
A0
H
H
L
L
DQ15
DQ8
22h
22h
ID
IH
to
X
X
X
X
X
(unprotected)
(protected)
DQ7
DQ0
01h
51h
51h
57h
57h
01h
00h
21526B-6
to
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