M29W320ET Datasheet, PDF (40/46 Pages) STMicroelectronics – 32 Mbit (4Mb x8 or 2Mb x16, Boot Block) 3V Supply Flash Memory

M29W320ET, M29W320EB
APPENDIX D. BLOCK PROTECTION
Block protection can be used to prevent any oper-
ation from modifying the data stored in the memo-
ry. The blocks are protected in groups, refer to
APPENDIX A., Table 20. and Table 21. for details
of the Protection Groups. Once protected, Pro-
gram and Erase operations within the protected
group 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.
Programmer Technique
The Programmer technique uses high (V_ID) volt-
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 group of blocks follow the flowchart in
Figure 20., Programmer Equipment Block Protect
Flowchart. To unprotect the whole chip it is neces-
sary to protect all of the groups first, then all
groups can be unprotected at the same time. To
unprotect the chip follow Figure 21., Programmer
Equipment Chip Unprotect Flowchart. Table
29., Programmer Technique Bus Operations,
BYTE = V_IH or V_IL, gives a summary of each oper-
ation.
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⁽¹⁾. This can be achieved without violating
the maximum ratings of the components on the mi-
croprocessor bus, therefore this technique is suit-
able for use after the memory has been fitted to
the system.
To protect a group of blocks follow the flowchart in
Figure 22., In-System Equipment Group Protect
Flowchart. To unprotect the whole chip it is neces-
sary to protect all of the groups first, then all the
groups can be unprotected at the same time. To
unprotect the chip follow Figure 23., In-System
Equipment Chip Unprotect Flowchart.
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.
Note: 1. RP can be either at V_IH or at V_ID when using the In-Sys-
tem Technique to protect the Extended Block.
Table 29. Programmer Technique Bus Operations, BYTE = V_IH or V_IL
Operation
EG
W
Address Inputs
A0-A20
Block (Group)
Protect⁽¹⁾
V_IL V_ID V_IL Pulse
A9 = V_ID, A12-A20 Block Address
Others = X
Chip Unprotect
V_ID V_ID V_IL Pulse
A9 = V_ID, A12 = V_IH, A15 = V_IH
Others = X
Block (Group)
Protection Verify
V_IL V_IL
A0 = V_IL, A1 = V_IH, A6 = V_IL, A9 = V_ID,
V_IH
A12-A20 Block Address
Others = X
Block (Group)
Unprotection Verify
V_IL V_IL
A0 = V_IL, A1 = V_IH, A6 = V_IH, A9 = V_ID,
V_IH
A12-A20 Block Address
Others = X
Note: 1. Block Protection Groups are shown in APPENDIX A., Table 20. and Table 21.
Data Inputs/Outputs
DQ15A–1, DQ14-DQ0
X
X
Pass = XX01h
Retry = XX00h
Retry = XX01h
Pass = XX00h
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