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 all
the time during read operation. 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
addresses 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
See "Reading Array Data" for more information. Refer to the
AC Read Operations table for timing specifications and to
the Read Operations Timings diagram for the timing
waveforms, lCC1 in the DC Characteristics table represents
the active current specification for reading array data.
Writing Commands/Command Sequences
To write a command or command sequence (which
includes programming data to the device and erasing
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. The Sector
Address Tables indicate the address range that each sector
occupies. A "sector address" consists of the address inputs
required to uniquely select a sector. See the "Command
Definitions" section for 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 I/O7 - I/O0. Standard
read cycle timings apply in this mode. Refer to the
"Autoselect Mode" and "Autoselect Command Sequence"
sections for more information.
ICC2 in the Characteristics table represents the active
current specification for the write mode. The "AC
Characteristics" section contains timing specification tables
and timing diagrams for write operations.
Program and Erase Operation Status
During an erase or program operation, the system may
check the status of the operation by reading the status bits
on I/O7 - I/O0. Standard read cycle timings and ICC read
specifications apply. Refer to "Write Operation Status" for
more information, and to each AC Characteristics section
for timing diagrams.
When the system is not reading or writing to the device, it
can place the device in the standby mode. In this mode,
current consumption is greatly reduced, and the outputs are
placed in the high impedance state, independent of the OE
The device enters the CMOS standby mode when the CE
& RESET pins ( CE only on A290021) are both held at VCC
± 0.5V. (Note that this is a more restricted voltage range
than VIH.) The device enters the TTL standby mode when
CE is held at VIH, while RESET (Not available on
A290021) is held at VCC±0.5V. The device requires the
standard access time (tCE) before it is ready to read data.
If the device is deselected during erasure or programming,
the device draws active current until the operation is
ICC3 in the DC Characteristics tables represents the standby
Output Disable Mode
When the OE input is at VIH, output from the device is
disabled. The output pins are placed in the high impedance
RESET : Hardware Reset Pin (N/A on A290021)
The RESET pin provides a hardware method of resetting
the device to reading array data. When the system drives
the RESET pin low for at least a period of tRP, the device
immediately terminates any operation in progress, tristates
all data output pins, and ignores all read/write attempts 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.
The RESET pin may be tied to the system reset circuitry. A
system reset would thus also reset the Flash memory,
enabling the system to read the boot-up firmware from the
Refer to the AC Characteristics tables for RESET
parameters and diagram.
(February, 2002, Version 1.0)
AMIC Technology, Inc.