MX29LV004C T/B
REQUIREMENTS FOR READING ARRAY
DATA
To read array data from the outputs, the system must
drive the CE# and OE# pins to VIL. CE# is the power
control and selects the device. OE# is the output control
and gates array data to the output pins. WE# should remain
at VIH.
The internal state machine is set for reading array data
upon device power-up, or after a hardware reset. This
ensures that no spurious alteration of the memory content
occurs during the power transition. No command is
necessary in this mode to obtain array data. Standard
microprocessor read cycles that assert valid address on
the device address inputs produce valid data on the device
data outputs. The device remains enabled for read access
until the command register contents are altered.
STANDBY MODE
When using both pins of CE# and RESET#, the device
enter CMOS Standby with both pins held at Vcc
±
0.3V.
The RESET# pin is provided only for 40-pin TSOP pack-
age type. If CE# and RESET# are held at VIH, but not
within the range of VCC
±
0.3V, the device will still be in
the standby mode, but the standby current will be larger.
During Auto Algorithm operation, Vcc active current
(Icc2) is required even CE# = "H" until the operation is
completed. The device can be read with standard ac-
cess time (tCE) from either of these standby modes,
before it is ready to read data.
OUTPUT DISABLE
With the OE# input at a logic high level (VIH), output
from the devices are disabled. This will cause the output
pins to be in a high impedance state.
WRITE COMMANDS/COMMAND SEQUENCES
To program data to the device or erase sectors of memory
, the system must drive WE# and CE# to VIL, and OE#
to VIH.
An erase operation can erase one sector, multiple sectors
, or the entire device. Table indicates the address space
that each sector occupies. A "sector address" consists
of the address bits required to uniquely select a sector.
The "Writing specific address and data commands or
sequences into the command register initiates device
operations. Table 1 defines the valid register command
sequences. Writing incorrect address and data values or
writing them in the improper sequence resets the device
to reading array data. Section has details on erasing a
sector or the entire chip, or suspending/resuming the erase
operation.
After the system writes the autoselect command
sequence, the device enters the autoselect mode. The
system can then read autoselect codes from the internal
register (which is separate from the memory array) on
Q7-Q0. Standard read cycle timings apply in this mode.
Refer to the Autoselect Mode and Autoselect Command
Sequence section for more information.
ICC2 in the DC Characteristics table represents the active
current specification for the write mode. The "AC
Characteristics" section contains timing specification table
and timing diagrams for write operations.
RESET# OPERATION
(for 40-TSOP package type)
The RESET# pin provides a hardware method of resetting
the device to reading array data. When the RESET# pin
is driven low for at least a period of tRP, the device
immediately terminates any operation in progress,
tristates all output pins, and ignores all read/write
commands for the duration of the RESET# pulse. The
device also resets the internal state machine to reading
array data. The operation that was interrupted should be
reinitiated once the device is ready to accept another
command sequence, to ensure data integrity
Current is reduced for the duration of the RESET# pulse.
When RESET# is held at VSS±0.3V, the device draws
CMOS standby current (ICC4). If RESET# is held at VIL
but not within VSS±0.3V, the standby current will be
greater.
The RESET# pin may be tied to system reset circuitry.
A system reset would that also reset the Flash memory,
enabling the system to read the boot-up firm-ware from
the Flash memory.
If RESET# is asserted during a program or erase
operation, the RY/BY# pin remains a "0" (busy) until the
internal reset operation is complete, which requires a time
of tREADY (during Embedded Algorithms). The system
can thus monitor RY/BY# to determine whether the reset
P/N:PM1148
REV. 1.3, APR. 24, 2006
9
MCNIX [ MACRONIX INTERNATIONAL ]
