M29W128FL View Datasheet(PDF) - Numonyx -> Micron
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MFG CO.
'M29W128FL' PDF : 78 Pages View PDF
M29W128FH, M29W128FL
High Voltage Block Protection
Appendix D High Voltage Block Protection
The High Voltage Block Protection can be used to prevent any operation from modifying the
data stored in the memory. The blocks are protected in groups, refer to Appendix A: Block
addresses and Read/Modify Protection Groups, and Table 28 for details of the Protection
Groups. 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
Programmer technique, the In-System technique and Temporary Unprotection. Temporary
Unprotection is controlled by the Reset/Block Temporary Unprotection pin, RP; this is
described in the Signal Descriptions section.
To protect the Extended Memory Block issue the Enter Extended Block command and then
use either the Programmer or In-System technique. Once protected issue the Exit Extended
Block command to return to read mode. The Extended Memory Block protection is
irreversible, once protected the protection cannot be undone.
D.1
Programmer technique
The Programmer technique uses high (VID) voltage 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 18: Programmer equipment Group
Protect flowchart. To unprotect the whole chip it is necessary to protect all of the groups first,
then all groups can be unprotected at the same time. To unprotect the chip follow Figure 19:
Programmer equipment Chip Unprotect flowchart. Table 36: Programmer technique Bus
operations, 8-bit or 16-bit mode, 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.
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