LH28F800SGN-L70 データシートの表示（PDF） - Sharp Electronics
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LH28F800SGN-L70 Datasheet PDF : 42 Pages
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2 PRINCIPLES OF OPERATION
The LH28F800SG-L SmartVoltage flash memory
includes an on-chip WSM to manage block erase,
word write, and lock-bit configuration functions. It
allows for : 100% TTL-level control inputs, fixed
power supplies during block erasure, word write,
and lock-bit configuration, and minimal processor
overhead with RAM-like interface timings.
After initial device power-up or return from deep
power-down mode (see Table 2 "Bus Operations"),
the device defaults to read array mode. Manipulation
of external memory control pins allow array read,
standby, and output disable operations.
Status register and identifier codes can be
accessed through the CUI independent of the VPP
voltage. High voltage on VPP enables successful
block erasure, word writing, and lock-bit
configuration. All functions associated with altering
memory contents — block erase, word write, lock-
bit configuration, status, and identifier codes — are
accessed via the CUI and verified through the
status register.
Commands are written using standard micro-
processor write timings. The CUI contents serve as
input to the WSM, which controls the block erase,
word write, and lock-bit configuration. The internal
algorithms are regulated by the WSM, including
pulse repetition, internal verification, and margining
of data. Addresses and data are internally latched
during write cycles. Writing the appropriate
command outputs array data, accesses the
identifier codes, or outputs status register data.
Interface software that initiates and polls progress
of block erase, word write, and lock-bit configuration
can be stored in any block. This code is copied to
and executed from system RAM during flash
memory updates. After successful completion,
reads are again possible via the Read Array
command. Block erase suspend allows system
LH28F800SG-L (FOR SOP)
software to suspend a block erase to read/write
data from/to blocks other than that which is
suspended. Word write suspend allows system
software to suspend a word write to read data from
any other flash memory array location.
2.1 Data Protection
Depending on the application, the system designer
may choose to make the VPP power supply
switchable (available only when memory block
erases, word writes, or lock-bit configurations are
required) or hardwired to VPPH1/2/3. The device
accommodates either design practice and
encourages optimization of the processor-memory
interface.
When VPP ≤ VPPLK, memory contents cannot be
altered. The CUI, with two-step block erase, word
write, or lock-bit configuration command sequences,
provides protection from unwanted operations even
when high voltage is applied to VPP. All write
functions are disabled when VCC is below the write
lockout voltage VLKO or when RP# is at VIL. The
device’s block locking capability provides additional
protection from inadvertent code or data alteration
by gating erase and word write operations.
3 BUS OPERATION
The local CPU reads and writes flash memory in-
system. All bus cycles to or from the flash memory
conform to standard microprocessor bus cycles.
3.1 Read
Information can be read from any block, identifier
codes, or status register independent of the VPP
voltage. RP# can be at either VIH or VHH.
The first task is to write the appropriate read mode
command (Read Array, Read Identifier Codes, or
Read Status Register) to the CUI. Upon initial
device power-up or after exit from deep power-
down mode, the device automatically resets to read
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