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AT49F2048A Datasheet(PDF) 3 Page - ATMEL Corporation

Part No. AT49F2048A
Description  2-megabit 256K x 8/ 128K x 16 5-volt Only CMOS Flash Memory
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Maker  ATMEL [ATMEL Corporation]
Homepage  http://www.atmel.com
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AT49F2048A
3
returns to the read or standby mode, depending upon the
state of the control inputs. By applying a 12V
± 0.5V input
signal to the RESET pin, the boot block array can be repro-
grammed even if the boot block program lockout feature
has been enabled (see Boot Block Programming Lockout
Override section).
ERASURE: Before a byte or word can be reprogrammed, it
must be erased. The erased state of the memory bits is a
logic “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
EC.
CHIP ERASE: The entire device can be erased at one time
by using the 6-byte chip erase software code. After the chip
erase has been initiated, the device will internally time the
erase operation so that no external clocks are required.
The maximum time to erase the chip is t
EC.
If the boot block lockout has been enabled, the chip erase
will not erase the data in the boot block; it will erase the
main memory block and the parameter blocks only. After
the chip erase, the device will return to the read or standby
mode.
SECTOR ERASE: As an alternative to a full chip erase, the
device is organized into four sectors that can be individually
erased. There are two 4K word parameter block sections:
one 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 ris-
ing edge of WE of the sixth cycle. The erase operation is
internally controlled; it will automatically time to completion.
Whenever the main memory block is erased and repro-
grammed, the two parameter blocks should be erased and
reprogrammed before the main memory block is erased
again. Whenever a parameter block is erased and repro-
grammed, the other parameter block should be erased and
reprogrammed before the first parameter block is erased
again. Whenever the boot block is erased and repro-
grammed, the main memory block and the parameter
blocks should be erased and reprogrammed before the
boot block is erased again.
BYTE/WORD PROGRAMMING: Once a memory block is
erased, it is programmed (to a logic “0”) on a byte-by-byte
or word-by-word basis. Programming is accomplished via
the internal device command register and is a four-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
BP cycle time. The Data Polling feature may
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-
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 during the entire chip
erase, sector erase or word programming operation. 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” on page 5 (for hard-
ware operation) or “Software Product Identification
Entry/Exit” on page 10. The manufacturer and device
codes are the same for both modes.
DATA POLLING: The AT49F2048A features Data Polling
to indicate the end of a program cycle. During a program




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