M29W800DB STMICROELECTRONICS [STMicroelectronics], M29W800DB Datasheet - Page 36

• Manufacturer Part Number: M29W800DB
• Description: 8 Mbit (1Mb x8 or 512Kb x16, Boot Block) 3V Supply Flash Memory
• Manufacturer: STMICROELECTRONICS [STMicroelectronics]

M29W800DT, M29W800DB
APPENDIX C. BLOCK PROTECTION
Block protection can be used to prevent any oper-
ation from modifying the data stored in the Flash.
Each Block can be protected individually. Once
protected, Program and Erase operations on the
block fail to change the data.
There are three techniques that can be used to
control Block Protection, these are the Program-
mer technique, the In-System technique and Tem-
porary Unprotection. Temporary Unprotection is
controlled by the Reset/Block Temporary Unpro-
tection pin, RP; this is described in the Signal De-
scriptions section.
Unlike the Command Interface of the Program/
Erase Controller, the techniques for protecting and
unprotecting blocks change between different
Flash memory suppliers. For example, the tech-
niques for AMD parts will not work on STMicro-
electronics parts. Care should be taken when
changing drivers for one part to work on another.
Programmer Technique
The Programmer technique uses high (V
age levels on some of the bus pins. These cannot
be achieved using a standard microprocessor bus,
therefore the technique is recommended only for
use in Programming Equipment.
To protect a block follow the flowchart in
20., Programmer Equipment Block Protect Flow-
chart, To unprotect the whole chip it is necessary
to protect all of the blocks first, then all blocks can
be unprotected at the same time. To unprotect the
chip follow
Chip Unprotect
Table 29. Programmer Technique Bus Operations, BYTE = V
36/42
Block Protect
Chip Unprotect
Block Protection
Verify
Block Unprotection
Verify
Operation
Figure 21., Programmer Equipment
Flowchart.
V
V
V
V
E
ID
IL
IL
IL
Table 29., Programmer
V
V
V
V
G
ID
ID
IL
IL
V
V
IL
IL
V
V
W
Pulse
Pulse
IH
IH
ID
A0 = V
A0 = V
Figure
) volt-
A9 = V
A9 = V
IL
IL
A12-A18 Block Address
A12-A18 Block Address
, A1 = V
, A1 = V
ID
ID
Address Inputs
, A12-A18 Block Address
, A12 = V
Technique Bus Operations, BYTE = V
gives a summary of each operation.
The timing on these flowcharts is critical. Care
should be taken to ensure that, where a pause is
specified, it is followed as closely as possible. Do
not abort the procedure before reaching the end.
Chip Unprotect can take several seconds and a
user message should be provided to show that the
operation is progressing.
In-System Technique
The In-System technique requires a high voltage
level on the Reset/Blocks Temporary Unprotect
pin, RP. This can be achieved without violating the
maximum ratings of the components on the micro-
processor bus, therefore this technique is suitable
for use after the Flash has been fitted to the sys-
tem.
To protect a block follow the flowchart in
22., In-System Equipment Block Protect Flow-
chart. To unprotect the whole chip it is necessary
to protect all of the blocks first, then all the blocks
can be unprotected at the same time. To unprotect
the chip follow
Chip Unprotect
The timing on these flowcharts is critical. Care
should be taken to ensure that, where a pause is
specified, it is followed as closely as possible. Do
not allow the microprocessor to service interrupts
that will upset the timing and do not abort the pro-
cedure before reaching the end. Chip Unprotect
can take several seconds and a user message
should be provided to show that the operation is
progressing.
Others = X
Others = X
Others = X
Others = X
A0-A18
IH
IH
, A6 = V
, A6 = V
IH
, A15 = V
IH
IH
IL
or V
, A9 = V
, A9 = V
Flowchart.
Figure 23., In-System Equipment
IL
IH
ID
ID
,
,
DQ15A–1, DQ14-DQ0
Data Inputs/Outputs
Retry = XX00h
Retry = XX01h
Pass = XX01h
Pass = XX00h
X
X
IH
or V
Figure
IL
,