A25L40P Series
OPERATING FEATURES
Page Programming
Status Register
To program one data byte, two instructions are required: Write
Enable (WREN), which is one byte, and a Page Program (PP)
sequence, which consists of four bytes plus data. This is
followed by the internal Program cycle (of duration tPP).
To spread this overhead, the Page Program (PP) instruction
allows up to 256 bytes to be programmed at a time (changing
bits from 1 to 0), provided that they lie in consecutive
addresses on the same page of memory.
The Status Register contains a number of status and control
bits that can be read or set (as appropriate) by specific
instructions.
WIP bit. The Write In Progress (WIP) bit indicates whether
the memory is busy with a Write Status Register, Program or
Erase cycle.
WEL bit. The Write Enable Latch (WEL) bit indicates the
status of the internal Write Enable Latch, BP2, BP1, and BP0
bits. The Block Protect (BP2, BP1, BP0) bits are non-volatile.
They define the size of the area to be software protected
against Program and Erase instructions.
Sector Erase and Bulk Erase
The Page Program (PP) instruction allows bits to be reset
from 1 to 0. Before this can be applied, the bytes of memory
need to have been erased to all 1s (FFh). This can be
achieved, a sector at a time, using the Sector Erase (SE)
instruction, or throughout the entire memory, using the Bulk
Erase (BE) instruction. This starts an internal Erase cycle (of
duration tSE or tBE).
SRWD bit. The Status Register Write Disable (SRWD) bit is
operated in conjunction with the Write Protect ( ) signal.
W
The Status Register Write Disable (SRWD) bit and Write
Protect ( ) signal allow the device to be put in the Hardware
W
Protected mode. In this mode, the non-volatile bits of the
Status Register (SRWD, BP2, BP1, BP0) become read-only
bits.
The Erase instruction must be preceded by a Write Enable
(WREN) instruction.
Protection Modes
Polling During a Write, Program or Erase Cycle
The environments where non-volatile memory devices are
used can be very noisy. No SPI device can operate correctly
in the presence of excessive noise. To help combat this, the
A25L40P boasts the following data protection mechanisms:
Power-On Reset and an internal timer (tPUW) can provide
protection against inadvertant changes while the power
supply is outside the operating specification.
Program, Erase and Write Status Register instructions are
checked that they consist of a number of clock pulses that
is a multiple of eight, before they are accepted for
execution.
A further improvement in the time to Write Status Register
(WRSR), Program (PP) or Erase (SE or BE) can be achieved
by not waiting for the worst case delay (tW, tPP, tSE, or tBE). The
Write In Progress (WIP) bit is provided in the Status Register
so that the application program can monitor its value, polling it
to establish when the previous Write cycle, Program cycle or
Erase cycle is complete.
Active Power, Stand-by Power and Deep
Power-Down Modes
All instructions that modify data must be preceded by a
Write Enable (WREN) instruction to set the Write Enable
Latch (WEL) bit. This bit is returned to its reset state by
the following events:
When Chip Select ( ) is Low, the device is enabled, and in
S
the Active Power mode.
When Chip Select ( ) is High, the device is disabled, but
S
could remain in the Active Power mode until all internal cycles
have completed (Program, Erase, Write Status Register). The
device then goes in to the Stand-by Power mode. The device
consumption drops to ICC1.
- Power-up
- Write Disable (WRDI) instruction completion
- Write Status Register (WRSR) instruction completion
- Page Program (PP) instruction completion
The Deep Power-down mode is entered when the specific
instruction (the Enter Deep Power-down Mode (DP)
instruction) is executed. The device consumption drops
further to ICC2. The device remains in this mode until another
specific instruction (the Release from Deep Power-down
Mode and Read Electronic Signature (RES) instruction) is
executed.
All other instructions are ignored while the device is in the
Deep Power-down mode. This can be used as an extra
software protection mechanism, when the device is not in
active use, to protect the device from inadvertent Write,
Program or Erase instructions.
- Sector Erase (SE) instruction completion
- Bulk Erase (BE) instruction completion
The Block Protect (BP2, BP1, BP0) bits allow part of the
memory to be configured as read-only. This is the
Software Protected Mode (SPM).
The Write Protect (
) signal allows the Block Protect
W
(BP2, BP1, BP0) bits and Status Register Write Disable
(SRWD) bit to be protected. This is the Hardware
Protected Mode (HPM).
In addition to the low power consumption feature, the
Deep Power-down mode offers extra software protection
from inadvertant Write, Program and Erase instructions,
as all instructions are ignored except one particular
instruction (the Release from Deep Power-down
instruction).
PRELIMINARY (May, 2007, Version 0.4)
5
AMIC Technology Corp.
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