at49f4096 ATMEL Corporation, at49f4096 Datasheet - Page 3

• Manufacturer Part Number: at49f4096
• Description: At49f4096 4-megabit 256k X 16 5-volt Only Flash Memory
• Manufacturer: ATMEL Corporation

“1”. The entire device can be erased at one time by using a
6-byte software code.
After the software chip erase has been initiated, the device
will internally time the erase operation so that no external
clocks are required. The maximum time needed to erase
the whole chip is t
CHIP ERASE: If the boot block lockout has been enabled,
the Chip Erase function is disabled; sector erases for the
parameter blocks and main memory block will still operate.
After the full chip erase the device will return back to read
mode. Any command during chip erase will be ignored.
SECTOR ERASE: As an alternative to a full chip erase, the
device is organized into three sectors that can be individu-
ally erased. There are two 8K word parameter block sec-
tions and one sector consisting of the boot block and the
main memory array block. The Sector Erase command is a
six bus cycle operation. The sector address is latched on
the falling WE edge of the sixth cycle while the 30H data
input command is latched at the rising edge of WE. The
sector erase starts after the rising edge of WE of the sixth
cycle. The erase operation is internally controlled; it will
automatically time to completion. When the boot block pro-
gramming lockout feature is not enabled, the boot block
and the main memory block will erase together (from the
same sector erase command). Once the boot region has
been protected, only the main memory array sector will
erase when its sector erase command is issued. Whenever
a parameter block is erased and reprogrammed, the other
parameter block should be erased and reprogrammed
before the first parameter block is erased again.
WORD PROGRAMMING: Once a memory block is erased,
it is programmed (to a logical “0”) on a word-by-word basis.
Programming is accomplished via the internal device com-
mand register and is a 4 bus cycle operation. The device
will automatically generate the required internal program
pulses.
Any commands written to the chip during the embedded
programming cycle will be ignored. If a hardware reset hap-
pens during programming, the data at the location being
programmed will be corrupted. Please note that a data “0”
cannot be programmed back to a “1”; only erase operations
can convert “0”s to “1”s. Programming is completed after
the specified t
also be used to indicate the end of a program cycle.
BOOT BLOCK PROGRAMMING LOCKOUT: The device
has one designated block that has a programming lockout
feature. This feature prevents programming of data in the
designated block once the feature has been enabled. The
size of the block is 8K words. This block, referred to as the
boot block, can contain secure code that is used to bring up
the system. Enabling the lockout feature will allow the boot
code to stay in the device while data in the rest of the
device is updated. This feature does not have to be acti-
BP
cycle time. The DATA polling feature may
EC
.
vated; the boot block’s usage as a write protected region is
optional to the user. The address range of the boot block is
00000H to 01FFFH.
Once the feature is enabled, the data in the boot block can
no longer be erased or programmed when input levels of
5.5V or less are used. Data in the main memory block can
still be changed through the regular programming method.
To activate the lockout feature, a series of six program
commands to specific addresses with specific data must be
performed. Please refer to the Command Definitions table.
BOOT BLOCK LOCKOUT DETECTION: A software
method is available to determine if programming of the boot
block section is locked out. When the device is in the soft-
ware product identification mode (see Software Product
Identification Entry and Exit sections) a read from address
location 00002H will show if programming the boot block is
locked out. If the data on I/O0 is low, the boot block can be
programmed; if the data on I/O0 is high, the program lock-
out feature has been enabled and the block cannot be pro-
grammed. The software product identification exit code
should be used to return to standard operation.
BOOT BLOCK PROGRAMMING LOCKOUT OVERRIDE:
The user can override the boot block programming lockout
by taking the RESET pin to 12 volts. By doing this pro-
tected boot block data can be altered through a chip erase,
sector erase or word programming. When the RESET pin is
brought back to TTL levels the boot block programming
lockout feature is again active.
PRODUCT IDENTIFICATION: The product identification
mode identifies the device and manufacturer as Atmel. It
may be accessed by hardware or software operation. The
hardware operation mode can be used by an external pro-
grammer to identify the correct programming algorithm for
the Atmel product.
For details, see Operating Modes (for hardware operation)
or Software Product Identification. The manufacturer and
device code is the same for both modes.
DATA POLLING: The AT49F4096 features DATA polling
to indicate the end of a program cycle. During a program
cycle an attempted read of the last byte loaded will result in
the complement of the loaded data on I/O7. Once the pro-
gram cycle has been completed, true data is valid on all
outputs and the next cycle may begin. During a chip or sec-
tor erase operation, an attempt to read the device will give
a “0” on I/O7. Once the program or erase cycle has com-
pleted, true data will be read from the device. DATA polling
may begin at any time during the program cycle.
TOGGLE BIT: In addition to DATA polling the AT49F4096
provides another method for determining the end of a pro-
gram or erase cycle. During a program or erase operation,
successive attempts to read data from the device will result
in I/O6 toggling between one and zero. Once the program
cycle has completed, I/O6 will stop toggling and valid data
3