AT49BV16X4 Datasheet, PDF (4/18 Pages) ATMEL Corporation – 16-megabit (1M x 16/2M x 8) 3-volt Only Flash Memory

The command sequences are written by applying a low
pulse on the WE or CE input with CE or WE low (respec-
tively) and OE high. The address is latched on the falling
edge of CE or WE, whichever occurs last. The data is
latched by the first rising edge of CE or WE. Standard
microprocessor write timings are used. The address loca-
tions used in the command sequences are not affected by
entering the command sequences.
RESET: A RESET input pin is provided to ease some sys-
tem applications. When RESET is at a logic high level, the
device is in its standard operating mode. A low level on the
RESET input halts the present device operation and puts
the outputs of the device in a high impedance state. When
a high level is reasserted on the RESET pin, the device
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 any sector can be reprogrammed
even if the sector lockout feature has been enabled (see
Sector Programming Lockout Override section).
ERASURE: Before a byte/word can be reprogrammed, it
must be erased. The erased state of memory bits is a logi-
cal “1”. The entire device can be erased by using the Chip
Erase command or individual sectors can be erased by
using the Sector Erase commands.
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 sector lockout has been enabled, the Chip Erase will
not erase the data in the sector that has been locked; it will
erase only the unprotected sectors. 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 forty sectors (SA0 - SA39) that can
be individually erased. 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 on 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 automati-
cally time to completion. The maximum time to erase a
section is t_SEC. When the sector programming lockout fea-
ture is not enabled, the sector will erase (from the same
sector erase command). Once a sector has been pro-
tected, data in the protected sectors cannot be changed
unless the RESET pin is taken to 12V ± 0.5V. An attempt to
erase a sector that has been protected will result in the
operation terminating in 2 µs.
BYTE/WORD PROGRAMMING: Once a memory block is
erased, it is programmed (to a logical “0”) on a byte-by-byte
or on a word-by-word basis. Programming is accomplished
via the internal device command 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_BP cycle time. The DATA polling feature or
the toggle bit feature may be used to indicate the end of a
program cycle.
SECTOR PROGRAMMING LOCKOUT: Each sector has a
programming lockout feature. This feature prevents pro-
gramming of data in the designated sectors once the
feature has been enabled. These sectors 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 activated; any sector’s usage
as a write protected region is optional to the user.
Once the feature is enabled, the data in the protected sec-
tors can no longer be erased or programmed when input
levels of 5.5V or less are used. Data in the remaining sec-
tors can still be changed through the regular programming
method. To activate the lockout feature, a series of six pro-
gram commands to specific addresses with specific data
must be performed. Please refer to the Command Defini-
tions table.
SECTOR LOCKOUT DETECTION: A software method is
available to determine if programming of a sector is locked
out. When the device is in the software product identifica-
tion mode (see Software product Identification Entry and
Exit sections) a read from address location 00002H within a
sector will show if programming the sector is locked out. If
the data on I/O0 is low, the sector can be programmed; if
the data on I/O0 is high, the program lockout feature has
been enabled and the sector cannot be programmed. The
software product identification exit code should be used to
return to standard operation.
SECTOR PROGRAMMING LOCKOUT OVERRIDE: The
user can override the sector programming lockout by taking
the RESET pin to 12V ± 0.5V. By doing this protected data
can be altered through a chip erase, sector erase or
byte/word programming. When the RESET pin is brought
back to TTL levels the sector programming lockout feature
is again active.
ERASE SUSPEND/ERASE RESUME: The erase suspend
command allows the system to interrupt a sector erase
operation and then program or read data from a different
sector within the same plane. Since this device has a dual
plane architecture, there is no need to use the erase
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AT49BV1604(T)/1614(T)