AT49F1604 Просмотр технического описания (PDF) - Atmel Corporation
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AT49F1604 Datasheet PDF : 18 Pages
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low pulse on the WE or CE input with CE or WE low
(respectively) 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”. Individual sectors can be erased by using the
Sector Erase command.
SECTOR ERASE: The device is organized into 40 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 con-
trolled; it will automatically time to completion. The
maximum time to erase a section is tSEC. When the sector
programming lockout feature is not enabled, the sector will
erase (from the same Sector Erase command). Once a
sector has been protected, 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 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 tBP cycle time. The Data Polling feature or the
Toggle Bit feature may be used to indicate the end of a pro-
gram 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 sector erase or byte/word pro-
gramming. When the RESET pin is brought back to TTL
levels, the sector programming lockout feature is again
active.
ERASE SUSPEND/ERASE RESUME: The Erase Sus-
pend command allows the system to interrupt a sector
erase operation and then program or read data from a dif-
ferent sector within the same plane. Since this device has a
dual-plane architecture, there is no need to use the Erase
Suspend feature while erasing a sector when you want to
read data from a sector in the other plane. After the Erase
Suspend command is given, the device requires a maxi-
mum time of 15 µs to suspend the erase operation. After
the erase operation has been suspended, the plane that
contains the suspended sector enters the erase-suspend-
read mode. The system can then read data or program
data to any other sector within the device. An address is
not required during the Erase Suspend command. During
a sector erase suspend, another sector cannot be erased.
To resume the sector erase operation, the system must
write the Erase Resume command. The Erase Resume
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AT49F1604(T)/1614(T)
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