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关 键 词：服务器存储数据恢复
行 业：电子 电子产品设计
发布时间：2021-04-12
4-megabit
2.5-volt or
2.7-volt
DataFlash®
AT45DB041B
For New
Designs Use
AT45DB041D
1. Description
The AT45DB041B is an SPI compatible serial interface Flash memory ideally suited
for a wide variety of digital voice-, image-, program code- and data-storage applications. Its 4,325,376 bits of memory are organized as 2048 pages of 264 bytes each. In
addition to the main memory, the AT45DB041B also contains two SRAM data buffers
of 264 bytes each.
The buffers allow receiving of data while a page in the main memory is being reprogrammed, as well as reading or writing a continuous data stream. EEPROM emulation
(bit or byte alterability) is easily handled with a self-contained three step Read-ModifyWrite operation. Unlike conventional Flash memories that are accessed randomly with
multiple address lines and a parallel interface, the DataFlash uses a SPI serial interface to sequentially access its data. DataFlash supports SPI mode 0 and mode 3. The
simple serial interface facilitates hardware layout, increases system reliability, minimizes switching noise, and reduces package size and active pin count. The device is
optimized for use in many commercial and industrial applications where high density,
low pin count, low voltage, and low power are essential. The device operates at clock
frequencies up to 20 MHz with a typical active read current consumption of 4 mA.
To allow for simple in-system reprogrammability, the AT45DB041B does not require
high input voltages for programming. The device operates from a single power supply,
2.5V to 3.6V or 2.7V to 3.6V, for both the program and read operations. The
AT45DB041B is enabled through the chip select pin (CS) and accessed via a threewire interface consisting of the Serial Input (SI), Serial Output (SO), and the Serial
Clock (SCK).
All programming cycles are self-timed, and no separate erase cycle is required before
programming
Pin Name Function
CS Chip Select
SCK Serial Clock
SI Serial Input
SO Serial Output
WP Hardware Page Write Protect Pin
The CS pin must remain low during the loading of the opcode, the address bits, the don’t care
bits, and the reading of data. When the end of a page in main memory is reached during a Continuous Array Read, the device will continue reading at the beginning of the next page with no
delays incurred during the page boundary crossover (the crossover from the end of one page to
the beginning of the next page).
A low-to-high transition on the CS pin will terminate the read operation and tri-state the SO pin.
The maximum SCK frequency allowable for the Continuous Array Read is defined by the fCAR
specification. The Continuous Array Read bypasses both data buffers and leaves the contents
of the buffers unchanged.
5.1.2 Main Memory Page Read
A Main Memory Page Read allows the user to read data directly from any one of the 2048 pages
in the main memory, bypassing both of the data buffers and leaving the contents of the buffers
unchanged. To start a page read, an opcode of 52H or D2H must be clocked into the device followed by 24 address bits and 32 don’t care bits. The first four bits of the 24-bit address
sequence are reserved bits, the next 11 address bits (PA10 - PA0) specify the page address,
and the next nine address bits (BA8 - BA0) specify the starting byte address within the page.
The 32 don’t care bits which follow the 24 address bits are sent to initialize the read operation.
Following the 32 don’t care bits, additional pulses on SCK result in serial data being output on
the SO (serial output) pin. The CS pin must remain low during the loading of the opcode, the
address bits, the don’t care bits, and the reading of data. When the end of a page in main memory is reached during a Main Memory Page Read, the device will continue reading at the
beginning of the same page. A low-to-high transition on the CS pin will terminate the read operation and tri-state the SO pin.
Buffer Read
Data can be read from either one of the two buffers, using different opcodes to specify which
buffer to read from. An opcode of 54H or D4H is used to read data from buffer 1, and an opcode
of 56H or D6H is used to read data from buffer 2. To perform a Buffer Read, the eight bits of the
opcode must be followed by 15 don’t care bits, nine address bits, and eight don’t care bits. Since
the buffer size is 264 bytes, nine address bits (BFA8 - BFA0) are required to specify the first byte
of data to be read from the buffer. The CS pin must remain low during the loading of the opcode,
the address bits, the don’t care bits, and the reading of data. When the end of a buffer is
reached, the device will continue reading back at the beginning of the buffer. A low-to-high transition on the CS pin will terminate the read operation and tri-state the SO pin.
Status Register Read
The status register can be used to determine the device’s Ready/Busy status, the result of a
Main Memory Page to Buffer Compare operation, or the device density. To read the status register, an opcode of 57H or D7H must be loaded into the device. After the last bit of the opcode is
shifted in, the eight bits of the status register, starting with the MSB (bit 7), will be shifted out on
the SO pin during the next eight clock cycles. The five most significant bits of the status register
will contain device information, while the remaining three least-significant bits are reserved for
future use and will have undefined values. After bit 0 of the status register has been shifted out,
the sequence will repeat itself (as long as CS remains low and SCK is being toggled) starting
again with bit 7. The data in the status register is constantly updated, so each repeating
sequence will output new data.
