E
SMART 3 ADVANCED BOOT BLOCK
3.1.1
READ
If RP# is taken low for time tPLPH during a program
or erase operation, the operation will be aborted
and the memory contents at the aborted location
(for a program) or block (for an erase) are no longer
valid, since the data may be partially erased or
written. The abort process goes through the
following sequence: When RP# goes low, the
device shuts down the operation in progress, a
process which takes time tPLRH to complete. After
this time tPLRH, the part will either reset to read
The flash memory has four read modes available:
read array, read identifier, read status and read
query. These modes are accessible independent of
the VPP voltage. The appropriate Read Mode
command must be issued to the CUI to enter the
corresponding mode. Upon initial device power-up
or after exit from reset, the device automatically
defaults to read array mode.
array mode (if RP# has gone high during tPLRH
,
CE# and OE# must be driven active to obtain data
at the outputs. CE# is the device selection control;
when active it enables the flash memory device.
OE# is the data output control and it drives the
selected memory data onto the I/O bus. For all read
modes, WE# and RP# must be at VIH. Figure 7
illustrates a read cycle.
Figure 9B) or enter reset mode (if RP# is still logic
low after tPLRH, Figure 9C). In both cases, after
returning from an aborted operation, the relevant
time tPHQV or tPHWL/tPHEL must be waited before a
read or write operation is initiated, as discussed in
the previous paragraph. However, in this case,
these delays are referenced to the end of tPLRH
rather than when RP# goes high.
3.1.2
OUTPUT DISABLE
As with any automated device, it is important to
assert RP# during system reset. When the system
comes out of reset, processor expects to read from
the flash memory. Automated flash memories
provide status information when read during
program or block erase operations. 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.
With OE# at a logic-high level (VIH), the device
outputs are disabled. Output pins are placed in a
high-impedance state.
3.1.3
STANDBY
Deselecting the device by bringing CE# to a logic-
high level (VIH) places the device in standby mode,
which substantially reduces device power
consumption without any latency for subsequent
read accesses. In standby, outputs are placed in a
high-impedance state independent of OE#. If
deselected during program or erase operation, the
device continues to consume active power until the
program or erase operation is complete.
3.1.5
WRITE
A write takes place when both CE# and WE# are
low and OE# is high. Commands are written to the
Command User Interface (CUI) using standard
microprocessor write timings to control flash
operations. The CUI does not occupy an
addressable memory location. The address and
data buses are latched on the rising edge of the
second WE# or CE# pulse, whichever occurs first.
Figure 8 illustrates a program and erase operation.
The available commands are shown in Table 6, and
3.1.4
DEEP POWER-DOWN / RESET
From read mode, RP# at VIL for time tPLPH
deselects the memory, places output drivers in a
high-impedance state, and turns off all internal
circuits. After return from reset, a time tPHQV is
required until the initial read access outputs are
valid. A delay (tPHWL or tPHEL) is required after
return from reset before a write can be initiated.
After this wake-up interval, normal operation is
restored. The CUI resets to read array mode, and
the status register is set to 80H. This case is shown
in Figure 9A.
Appendix
A provides detailed information on
moving between the different modes of operation
using CUI commands.
13
PRELIMINARY
INTEL [ INTEL ]
