A29400 Series
Word/Byte Configuration
The
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.
pin determines whether the I/O pins I/O15-I/O0
BYTE
operate in the byte or word configuration. If the
pin
BYTE
is set at logic ”1”, the device is in word configuration, I/O15-
I/O0 are active and controlled by and
.
OE
CE
If the
pin is set at logic “0”, the device is in byte
BYTE
configuration, and only I/O0-I/O7 are active and controlled
by and . I/O8-I/O14 are tri-stated, and I/O15 pin is
Standby Mode
CE
OE
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
used as an input for the LSB(A-1) address function.
Requirements for Reading Array Data
To read array data from the outputs, the system must drive
input.
OE
the
and
pins to VIL.
is the power control and
CE
OE
CE
The device enters the CMOS standby mode when the
CE
pins are both held at VCC ± 0.5V. (Note that this
selects the device.
is the output control and gates
OE
array data to the output pins.
&
RESET
is a more restricted voltage range than VIH.) The device
enters the TTL standby mode when is held at VIH,
should remain at VIH all
WE
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 altered.
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.
CE
is held at VCC±0.5V. The device requires the
while
RESET
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
completed.
ICC3 in the DC Characteristics tables represents the standby
current specification.
Output Disable Mode
When the
input is at VIH, output from the device is
OE
disabled. The output pins are placed in the high impedance
state.
: Hardware Reset Pin
RESET
The
Writing Commands/Command Sequences
pin provides a hardware method of resetting
RESET
the device to reading array data. When the system drives
the pin low for at least a period of tRP, the device
To write a command or command sequence (which
includes programming data to the device and erasing
RESET
sectors of memory), the system must drive
and
CE
WE
immediately terminates any operation in progress, tristates
all data output pins, and ignores all read/write attempts for
to VIL, and
to VIH. An erase operation can erase one
OE
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.
the duration of the
pulse. The device also resets
RESET
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
pin may be tied to the system reset circuitry.
RESET
A system reset would thus also reset the Flash memory,
enabling the system to read the boot-up firmware from the
Flash memory.
Refer to the AC Characteristics tables for
parameters and diagram.
RESET
ICC2 in the DC 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.
PRELIMINARY
(February, 2001, Version 0.1)
5
AMIC Technology, Inc.