N25Q128 Datasheet, PDF (103/185 Pages) Numonyx B.V – 128-Mbit, 1.8 V, multiple I/O, 4-Kbyte subsector erase on boot sectors, XiP enabled, serial flash memory with 108 MHz SPI bus interface

N25Q128 - 1.8 V
Instructions
status register (WRSR) instruction is not executed once the hardware protected mode
(HPM) is entered.
Figure 31. Write Status Register instruction sequence
S
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
C
Instruction
Status
register in
DQ0
76543210
DQ1
High Impedance
MSB
AI13735
The protection features of the device are summarized in Table 8.
When the Status Register Write Disable (SRWD) bit of the Status Register is 0 (its initial
delivery state), it is possible to write to the Status Register provided that the Write Enable
Latch (WEL) bit has previously been set by a Write Enable (WREN) instruction, regardless
of the whether Write Protect (W/VPP) is driven High or Low.
When the Status Register Write Disable (SRWD) bit of the Status Register is set to '1', two
cases need to be considered, depending on the state of Write Protect (W/VPP):
„ If Write Protect (W/VPP) is driven High, it is possible to write to the Status Register
provided that the Write Enable Latch (WEL) bit has previously been set by a Write
Enable (WREN) instruction.
„ If Write Protect (W/VPP) is driven Low, it is not possible to write to the Status Register
even if the Write Enable Latch (WEL) bit has previously been set by a Write Enable
(WREN) instruction (attempts to write to the Status Register are rejected, and are not
accepted for execution). As a consequence, all the data bytes in the memory area that
are software protected (SPM) by the Block Protect (BP3, BP2, 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 in either of the following ways:
„ setting the Status Register Write Disable (SRWD) bit after driving Write Protect
(W/VPP) Low
„ driving Write Protect (W/VPP) 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/VPP) High.
If Write Protect (W/VPP) is permanently tied High, the Hardware Protected mode (HPM) can
never be activated, and only the Software Protected mode (SPM), using the Block Protect
(BP3, BP2, BP1, BP0) bits of the Status Register, can be used.
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