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28F004S5 SMART 5 FlashFile™ MEMORY FAMILY 4, 8, AND 16 MBIT Intel
Intel Intel
28F004S5 Datasheet PDF : 37 Pages
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BYTE-WIDE SMART 5 FlashFile™ MEMORY FAMILY
E
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, programs, or lock-bit configurations are
required) or hardwired to VPPH1/2. The device
accommodates either design practice and
encourages optimization of the processor-memory
interface.
When VPP VPPLK, memory contents cannot be
altered. When high voltage is applied to VPP, the
two-step block erase, program, or lock-bit
configuration command sequences provides pro-
tection from unwanted operations. All write
functions are disabled when VCC voltage 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 program operations.
3.0 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
Block information, identifier codes, or status register
can be read 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
array mode. Four control pins dictate the data flow
in and out of the component: CE#, OE#, WE#, and
RP#. CE# and OE# must be driven active to obtain
data at the outputs. CE# is the device selection
control, and when active enables the selected
memory device. OE# is the data output (DQ0–DQ7)
control and when active drives the selected
memory data onto the I/O bus. WE# must be at VIH
and RP# must be at VIH or VHH. Figure 15
illustrates a read cycle.
10
3.2 Output Disable
With OE# at a logic-high level (VIH), the device
outputs are disabled. Output pins DQ0–DQ7 are
placed in a high-impedance state.
3.3 Standby
CE# at a logic-high level (VIH) places the device in
standby mode which substantially reduces device
power consumption. DQ0–DQ7 outputs are placed
in a high-impedance state independent of OE#. If
deselected during block erase, program, or
lock-bit configuration, the device continues
functioning and consuming active power until the
operation completes.
3.4 Deep Power-Down
RP# at VIL initiates the deep power-down mode.
In read mode, RP#-low deselects the memory,
places output drivers in a high-impedance state,
and turns off all internal circuits. RP# must be held
low for time tPLPH. Time tPHQV is required after
return from power-down until initial memory access
outputs are valid. After this wake-up interval,
normal operation is restored. The CUI resets to
read array mode, and the status register is set to
80H.
During block erase, program, or lock-bit
configuration, RP#-low will abort the operation.
RY/BY# remains low until the reset operation is
complete. Memory contents being altered are no
longer valid; the data may be partially erased or
written. Time tPHWL is required after RP# goes to
logic-high (VIH) before another command can be
written.
As with any automated device, it is important to
assert RP# during system reset. When the system
comes out of reset, it expects to read from the flash
memory. Automated flash memories provide status
information when accessed during block erase,
program, or lock-bit configuration modes. If a CPU
reset occurs with no flash memory reset, proper
CPU initialization may not occur because the flash
memory may be providing status information
instead of array data. Intel’s flash memories allow
proper CPU initialization following a system reset
through the use of the RP# input. In this application,
RP# is controlled by the same RESET# signal that
resets the system CPU.
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