AT45DB321C Datasheet, PDF (13/37 Pages) ATMEL Corporation – 32 MEGABIT 2.7 VOLT DATAFLASH

AT45DB321C [Preliminary]
Pin Descriptions
1
WP
progress, modes in Group B can be started, except the first two Group A commands
(Memory Array Read Commands).
This gives the 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.
SERIAL INPUT (SI): The SI pin is an input-only pin and is used to shift data serially 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 seri-
ally out from the device.
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 input pin (SI), and the output pin
(SO) 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 transition on the CS pin is required to
end an operation or to start an internally self-timed operation.
WRITE PROTECT (WP): The WP pin is used to control the Hardware Sector Protection.
Hardware Sector Protection is enabled by asserting the WP pin and keeping the pin in
it’s asserted state. Disabling Hardware Sector Protection is accomplished by simply
deasserting the WP pin. The WP pin will override the software controlled sector protec-
tion method but only for protecting the sectors. For example, if the sectors were not
previously protected by the Enable Sector Protection command, then simply asserting
the WP pin for the minimum specified time (t_WPE) would enable the sector protection.
When the WP pin is deasserted; however, the sector protection would no longer be
enabled as long as the Enable Sector Protection command was not issued while the WP
pin was asserted. If the Enable Sector Protection command was issued before or while
the WP pin was asserted, then simply deasserting the WP pin would not disable the sec-
tor protection. In this case, the Disable Sector Protection command would need to be
issued while the WP pin is deasserted to disable the sector protection. The Disable Sec-
tor Protection command is also ignored whenever the WP pin is asserted.
To ensure backwards compatibility with previous generations of DataFlash, the function
of the WP pin has not changed. Therefore, when the WP pin is asserted, certain sectors
in the memory array will be protected, and when the WP pin is deasserted, the memory
array will be unprotected provided the Enable Sector Protection command hasn’t been
issued. New devices are shipped from Atmel with the contents of the Sector Protection
Register pre-programmed so that sectors 0a and 0b are specified for protection while
the remaining sectors are not flagged for protection. The user can reprogram the Sector
Protection Register to change which sectors will be protected by the WP pin.
The table below details the sector protection status for various scenarios of the WP pin,
the Enable Sector Protection command, and the Disable Sector Protection command.
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3
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3387B–DFLSH–9/04