BYTE-WIDE SMART 3 FlashFile MEMORY FAMILY
E
12
PRELIMINARY
2.1
Data Protection
Depending on the application, the system designer
may choose to make the V
PP
power supply
switchable (available only when memory block
erase, program, or lock-bit configuration operations
are required) or hardwired to V
PPH1/2
. The device
accommodates
either
encourages optimization of the processor-memory
interface.
design
practice
and
When V
PP
≤
V
PPLK
, memory contents cannot be
altered. When high voltage is applied to V
PP
, the
two-step
block
erase,
configuration command sequences provides pro-
tection from unwanted operations. All write
functions are disabled when V
CC
voltage is below
the write lockout voltage V
LKO
or when RP# is at
V
IL
. The device’s block locking capability provides
additional protection from inadvertent code or data
alteration by gating erase and program operations.
program,
or
lock-bit
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 V
PP
voltage. RP#
can be at either V
IH
or V
HH
.
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 (DQ
0
–DQ
7
)
control and when active drives the selected
memory data onto the I/O bus. WE# must be at V
IH
and RP# must be at V
IH
or V
HH
. Figure 17
illustrates a read cycle.
3.2
Output Disable
With OE# at a logic-high level (V
), the device
outputs are disabled. Output pins DQ
0
–DQ
7
are
placed in a high-impedance state.
3.3
Standby
CE# at a logic-high level (V
) places the device in
standby mode which substantially reduces device
power consumption. DQ
0
–DQ
7
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 V
IL
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 t
PLPH
. Time t
PHQV
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
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 t
PHWL
is required after RP# goes to
logic-high (V
IH
) before another command can be
written.
block
erase,
program,
or
lock-bit
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.