M29W641DH Datasheet, PDF (36/42 Pages) STMicroelectronics – 64 Mbit 4Mb x16, Uniform Block 3V Supply Flash Memory

M29W641DH, M29W641DL, M29W641DU
APPENDIX D. BLOCK PROTECTION
Block protection can be used to prevent any oper-
ation from modifying the data stored in the memo-
ry. Once protected, Program 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 16, Programmer Equipment Group 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 17, Programmer
Equipment Chip Unprotect Flowchart. Table 25,
Programmer Technique Bus Operations, 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 memory has been fitted to the sys-
tem.
To protect a group of blocks follow the flowchart in
Figure 18, 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 19, 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.
Table 25. Programmer Technique Bus Operations
Operation
EG
W
Address Inputs
A0-A21
Block (Group)
Protect⁽¹⁾
V_IL V_ID V_IL Pulse
A9 = V_ID, A12-A21 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-A21 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-A21 Block Address
Others = X
Note: 1. Block Protection Groups are shown in Appendix A, Tables 17.
Data Inputs/Outputs
DQ15-DQ0
X
X
Pass = XX01h
Retry = XX00h
Retry = XX01h
Pass = XX00h
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