M95256, M95128
(BP1, BP0) bits of the Status Register, are
also hardware protected against data
modification.
Regardless of the order of the two events, the
Hardware Protected Mode (HPM) can be entered:
– by setting the Status Register Write Disable
(SRWD) bit after driving Write Protect (W) Low
– or by driving Write Protect (W) Low after
setting the Status Register Write Disable
(SRWD) bit.
The only way to exit the Hardware Protected Mode
(HPM) once entered is to pull Write Protect (W)
High.
If Write Protect (W) is permanently tied High, the
Hardware Protected Mode (HPM) can never be
activated, and only the Software Protected Mode
(SPM), using the Block Protect (BP1, BP0) bits of
the Status Register, can be used.
Figure 11. Write Status Register (WRSR) Sequence
S
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
C
Instruction
Status
Register In
D
76543210
High Impedance
MSB
Q
AI02282D
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