4Mb
SMART 3 BOOT BLOCK FLASH MEMORY
PARAMETER BLOCKS
The two 8KB parameter blocks store less sensitive and
more frequently changing system parameters and also
may store configuration or diagnostic coding. These
blocks are enabled for erasure when the V
PP
pin is at V
PPH
.
No super-voltage unlock or WP# control is required.
MAIN MEMORY BLOCKS
The four remaining blocks are general-purpose
memory blocks and do not require a super-voltage on
RP# or WP# control to be erased or written. These blocks
are intended for code storage, ROM-resident applica-
tions or operating systems that require in-system update
capability.
latched on the falling edge of OE# or CE#, whichever
occurs last. If the contents of the status register change
during a READ of the status register, either OE# or CE#
may be toggled while the other is held LOW to update the
output.
Following a WRITE or ERASE, the device automati-
cally enters the status register read mode. In addition, a
READ during a WRITE or ERASE produces the status
register contents on DQ0–DQ7. When the device is in the
erase suspend mode, a READ operation produces the
status register contents until another command is is-
sued. In certain other modes, READ STATUS REGIS-
TER may be given to return to the status register read
mode. All commands and their operations are described
in the Command Set and Command Execution sections.
IDENTIFICATION REGISTER
A READ of the two 8-bit device identification registers
requires the same input sequencing as a READ of the
array. WE# must be HIGH, and OE# and CE# must be
LOW. However, ID register data is output only on DQ0–
DQ7, regardless of the condition of BYTE# on the
MT28F400B3. A0 is used to decode between the two bytes
of the device ID register; all other address inputs are
“Don’t Care.” When A0 is LOW, the manufacturer com-
patibility ID is output, and when A0 is HIGH, the device
ID is output. DQ8–DQ15 are High-Z when BYTE# is LOW.
When BYTE# is HIGH, DQ8–DQ15 are 00h when the
manufacturer compatibility ID is read and 44h when the
device ID is read.
To get to the identification register read mode, READ
IDENTIFICATION may be issued while the device is in
certain other modes. In addition, the identification regis-
ter read mode can be reached by applying a super-volt-
age (V
ID
) to the A9 pin. Using this method, the ID register
can be read while the device is in any mode. When A9 is
returned to V
IL
or V
IH
, the device returns to the previous
mode.
OUTPUT (READ) OPERATIONS
The MT28F004B3 and MT28F400B3 feature three dif-
ferent types of READs. Depending on the current mode of
the device, a READ operation produces data from the
memory array, status register or device identification
register. In each of these three cases, the WE#, CE# and
OE# inputs are controlled in a similar manner. Moving
between modes to perform a specific READ is described
in the Command Execution section.
MEMORY ARRAY
To read the memory array, WE# must be HIGH, and
OE# and CE# must be LOW. Valid data is output on the
DQ pins when these conditions have been met and a
valid address is given. Valid data remains on the DQ pins
until the address changes, or until OE# or CE# goes HIGH,
whichever occurs first. The DQ pins continue to output
new data after each address transition as long as OE# and
CE# remain LOW.
The MT28F400B3 features selectable bus widths.
When the memory array is accessed as a 256K x 16, BYTE#
is HIGH, and data is output on DQ0–DQ15. To access the
memory array as a 512K x 8, BYTE# must be LOW, DQ8–
DQ14 must be High-Z, and all data must be output on
DQ0–DQ7. The DQ15/A-1 pin becomes the lowest or-
der address input so that 524,288 locations can be read.
After power-up or RESET, the device is automatically
in the array read mode. All commands and their opera-
tions are described in the Command Set and Command
Execution sections.
STATUS REGISTER
Performing a READ of the status register requires the
same input sequencing as a READ of the array except that
the address inputs are “Don’t Care.” The status register
contents are always output on DQ0–DQ7, regardless of
the condition of BYTE# on the MT28F400B3. DQ8–DQ15
are LOW when BYTE# is HIGH, and DQ8–DQ14 are High-
Z when BYTE# is LOW. Data from the status register is
4Mb Smart 3 Boot Block Flash Memory
F45_3.p65 – Rev. 3, Pub. 12/01
INPUT OPERATIONS
The DQ pins are used either to input data to the array
or to input a command to the CEL. A command input
issues an 8-bit command to the CEL to control the mode
of operation of the device. A WRITE is used to input data
to the memory array. The following section describes
both types of inputs. More information describing how to
use the two types of inputs to write or erase the device is
provided in the Command Execution section.
COMMANDS
To perform a command input, OE# must be HIGH,
and CE# and WE# must be LOW. Addresses are “Don’t
Care” but must be held stable, except during an ERASE
CONFIRM (described in a later section). The 8-bit com-
9
Micron Technology, Inc., reserves the right to change products or specifications without notice.
©2001, Micron Technology, Inc.
MICRON [ MICRON TECHNOLOGY ]
