at45db021a ATMEL Corporation, at45db021a Datasheet - Page 7

• Manufacturer Part Number: at45db021a
• Description: 2-megabit 2.7-volt Only Serial Dataflash
• Manufacturer: ATMEL Corporation

of main memory. The operation is internally self-timed and
should take place in a maximum time of t
time, the status register will indicate that the part is busy.
If a sector is programmed or reprogrammed sequentially
page-by-page, then the programming algorithm shown in
Figure 1 on page 24 is recommended. Otherwise, if multi-
ple bytes in a page or several pages are programmed
randomly in a sector, then the programming algorithm
shown in Figure 2 on page 25 is recommended.
Operation Mode Summary
The modes described can be separated into two groups –
modes which make use of the Flash memory array (Group
A) and modes which do not make use of the Flash memory
array (Group B).
Group A modes consist of:
1. Main Memory Page Read
2. Main Memory Page to Buffer 1 (or 2) Transfer
3. Main Memory Page to Buffer 1 (or 2) Compare
4. Buffer 1 (or 2) to Main Memory Page Program with
5. Buffer 1 (or 2) to Main Memory Page Program
6. Page Erase
7. Block Erase
8. Main Memory Page Program through Buffer
9. Auto Page Rewrite
Group B modes consist of:
1. Buffer 1 (or 2) Read
2. Buffer 1 (or 2) Write
3. Status Register Read
If a Group A mode is in progress (not fully completed), then
another mode in Group A should not be started. However,
during this time in which a Group A mode is in progress,
modes in Group B can be started.
This gives the Serial DataFlash the ability to virtually
accommodate a continuous data stream. While data is
being programmed into main memory from buffer 1, data
can be loaded into buffer 2 (or vice versa). See application
note AN-4 (“Using Atmel’s Serial DataFlash”) for more
details.
Pin Descriptions
SERIAL INPUT (SI): The SI pin is an input-only pin and is
used to shift data into the device. The SI pin is used for all
data input, including opcodes and address sequences.
SERIAL OUTPUT (SO): The SO pin is an output-only pin
and is used to shift data out from the device.
Built-in Erase
without Built-in Erase
EP
. During this
SERIAL CLOCK (SCK): The SCK pin is an input-only pin
and is used to control the flow of data to and from the
DataFlash. Data is always clocked into the device on the
rising edge of SCK and clocked out of the device on the
falling edge of SCK.
CHIP SELECT (CS): The DataFlash is selected when the
CS pin is low. When the device is not selected, data will not
be accepted on the SI pin, and the SO pin will remain in a
high-impedance state. A high-to-low transition on the CS
pin is required to start an operation, and a low-to-high tran-
sition on the CS pin is required to end an operation.
WRITE PROTECT: If the WP pin is held low, the first 256
pages of the main memory cannot be reprogrammed. The
only way to reprogram the first 256 pages is to first drive
the protect pin high and then use the program commands
previously mentioned. The WP pin is internally pulled high;
therefore, connection of the WP pin is not necessary if this
pin and feature will not be utilized. However, it is recom-
mended that the WP pin be driven high externally
whenever possible.
RESET: A low state on the reset pin (RESET) will terminate
the operation in progress and reset the internal state
machine to an idle state. The device will remain in the reset
condition as long as a low level is present on the RESET
pin. Normal operation can resume once the RESET pin is
brought back to a high level.
The device incorporates an internal power-on reset circuit,
so there are no restrictions on the RESET pin during
power-on sequences. The RESET pin is also internally
pulled high; therefore, connection of the RESET pin is not
necessary if this pin and feature will not be utilized. How-
ever, it is recommended that the RESET pin be driven high
externally whenever possible.
READY/BUSY: This open-drain output pin will be driven
low when the device is busy in an internally self-timed oper-
ation. This pin, which is normally in a high state (through
a 1k Ω external pull-up resistor), will be pulled low during
programming operations, compare operations, and during
page-to-buffer transfers.
The busy status indicates that the Flash memory array and
one of the buffers cannot be accessed; read and write
operations to the other buffer can still be performed.
Power-on/Reset State
When power is first applied to the device, or when recover-
ing from a reset condition, the device will default to SPI
Mode 3. In addition, the SO pin will be in a high-impedance
state, and a high-to-low transition on the CS pin will be
required to start a valid instruction. The SPI mode will be
automatically selected on every falling edge of CS by
sampling the inactive clock state.
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