Rainbow Electronics AT45DB021D User Manual

Features

• Single 2.7V to 3.6V Supply

• RapidS Serial Interface: 66MHz Maximum Clock Frequency

– SPI Compatible Modes 0 and 3

• User Configurable Page Size

– 256-Bytes per Page – 264-Bytes per Page – Page Size Can Be Factory Pre-configured for 256-Bytes

• Page Program Operation

– Intelligent Programming Operation – 1,024 Pages (256/264-Bytes/Page) Main Memory

• Flexible Erase Options

– Page Erase (256-Bytes) – Block Erase (2-Kbytes) – Sector Erase (32-Kbytes) – Chip Erase (2-Mbits)

• One SRAM Data Buffer (256/264-Bytes)

• Continuous Read Capability through Entire Array

– Ideal for Code Shadowing Applications

• Low-power Dissipation

– 7mA Active Read Current Typical – 25µA Standby Current Typical – 15µA Deep Power-down Typical

• Hardware and Software Data Protection Features

– Individual Sector

• Sector Lockdown for Secure Code and Data Storage

– Individual Sector

• Security: 128-byte Security Register

– 64-byte User Programmable Space – Unique 64-byte Device Identifier

• JEDEC Standard Manufacturer and Device ID Read

• 100,000 Program/Erase Cycles Per Page Minimum

• Data Retention – 20 Years

• Industrial Temperature Range

• Green (Pb/Halide-free/RoHS Compliant) Packaging Options

2-megabit

2.7V Minimum DataFlash

AT45DB021D

Description

The AT45DB021D is a 2.7V, serial-interface Flash memory ideally suited for a wide variety of digital voice-, image-, program code- and data-storage applications. The AT45DB021D supports RapidS™serial interface for applications requiring very high speed operations. RapidS serial interface is SPI compatible for frequencies up to 66MHz. Its 2-,162-,688-bits of memory are organized as 1,024-pages of 256-bytes or 264-bytes each. In addition to the main memory, the AT45DB021D also contains one SRAM buffer of 256-/264-bytes. EEPROM emulation (bit or byte alterability) is easily handled with a self-contained three step read-modify-write operation. Unlike conventional Flash memories that are accessed randomly with multiple address lines and a parallel interface, the DataFlash®uses a RapidS serial interface to sequentially access its data. The simple sequential access dramatically reduces active pin count, facilitates hardware layout, increases system reliability, minimizes switching noise, and reduces package size.

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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.

To allow for simple in-system reprogrammability, the AT45DB021D does not require high input voltages for programming. The device operates from a single power supply, 2.7V to 3.6V, for both the program and read operations. The AT45DB021D is enabled through the chip select pin ( consisting of the Serial Input (SI), Serial Output (SO), and the Serial Clock (SCK).

All programming and erase cycles are self-timed.

1. Pin Configurations and Pinouts

Table 1-1. Pin Configurations

Symbol Name and Function

Chip Select: Asserting the CS pin selects the device. When the CS pin is deasserted, the device will be

deselected and normally be placed in the standby mode (not Deep Power-Down mode), and the output pin (SO) will be in a high-impedance state. When the device is deselected, data will not be accepted on

SCK

RESET

GND Ground: The ground reference for the power supply. GND should be connected to the system ground. –

the input pin (SI).

A high-to-low transition on the CS pin is required to start an operation, and a low-to-high transition is required to end an operation. When ending an internally self-timed operation such as a program or erase cycle, the device will not enter the standby mode until the completion of the operation.

Serial Clock: This pin is used to provide a clock to the device and is used to control the flow of data to and from the device. Command, address, and input data present on the SI pin is always latched on the rising edge of SCK, while output data on the SO pin is always clocked out on the falling edge of SCK.

Serial Input: The SI pin is used to shift data into the device. The SI pin is used for all data input including command and address sequences. Data on the SI pin is always latched on the rising edge of SCK.

Serial Output: The SO pin is used to shift data out from the device. Data on the SO pin is always clocked out on the falling edge of SCK.

Write Protect: When the WP pin is asserted, all sectors specified for protection by the Sector Protection Register will be protected against program and erase operations regardless of whether the Enable Sector Protection command has been issued or not. The WP pin functions independently of the software controlled protection method. After the WP pin goes low, the content of the Sector Protection Register cannot be modified.

If a program or erase command is issued to the device while the WP pin is asserted, the device will simply ignore the command and perform no operation. The device will return to the idle state once the CS pin has been deasserted. The Enable Sector Protection command and Sector Lockdown command, however, will be recognized by the device when the WP pin is asserted.

The WP pin is internally pulled-high and may be left floating if hardware controlled protection will not be used. However, it is recommended that the WP pin also be externally connected to VCCwhenever 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. If this pin and feature are not utilized it is recommended that the RESET pin be driven high externally.

Device Power Supply: The VCCpin is used to supply the source voltage to the device.

Operations at invalid VCCvoltages may produce spurious results and should not be attempted.

CS) and accessed via a three-wire interface

Asserte

d State Type

Low Input

– Input

– Output

Low Input

–Power

Groun

AT45DB021D

3638K–DFLASH–11/2012

AT45DB021D

Figure 1-1. SOIC Top View Figure 1-2. UDFN Top View

SCK

RESET

1 2 3 4

GND

VCC

SCK

RESET

(1)

GND

VCC

Notes: 1. The metal pad on the bottom of the UDFN package is floating. This pad can be a “No Connect” or connected to

GND

Figure 1-3. Block Diagram

FLASH MEMORY ARRAY

PAGE (256-/264-BYTES)

BUFFER (256-/264-BYTES)

SCK

RESET

VCC

GND

I/O INTERFACE

SO SI

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2. Memory Array

To provide optimal flexibility, the memory array of the AT45DB021D is divided into three levels of granularity comprising of sectors, blocks, and pages. The “Memory Architecture Diagram” illustrates the breakdown of each level and details the number of pages per sector and block. All program operations to the DataFlash occur on a page-by-page basis. The erase operations can be performed at the chip, sector, block or page level.

Figure 2-1. Memory Architecture Diagram

SECTOR ARCHITECTURE BLOCK ARCHITECTURE PAGE ARCHITECTURE

SECTOR 0a = 8 Pages

2,048/2,112-bytes

SECTOR 0a

BLOCK 0

BLOCK 1

BLOCK 2

8 Pages

PAGE 0

PAGE 1

SECTOR 0b = 120 Pages

31,744/32,726-bytes

SECTOR 1 = 128 Pages

32,768/33,792-bytes

SECTOR 6 = 128 Pages

32,768/33,792-bytes

SECTOR 7 = 128 Pages

32,768/33,792-bytes

3. Device Operation

The device operation is controlled by instructions from the host processor. The list of instructions and their associated opcodes are contained in Tables 13-1 through 13-7. A valid instruction starts with the falling edge of CS followed by the appropriate 8-bit opcode and the desired buffer or main memory address location. While the CS pin is low, toggling the SCK pin controls the loading of the opcode and the desired buffer or main memory address location through the SI (serial input) pin. All instructions, addresses, and data are transferred with the most significant bit (MSB) first.

SECTOR 0b

SECTOR 1

Block = 1,024/1,056-bytes

BLOCK 14

BLOCK 15

BLOCK 16

BLOCK 17

BLOCK 30

BLOCK 31

BLOCK 32

BLOCK 33

BLOCK 126

BLOCK 127

BLOCK 0

BLOCK 1

PAGE 6

PAGE 7

PAGE 8

PAGE 9

PAGE 14

PAGE 15

PAGE 16

PAGE 17

PAGE 18

PAGE 1,022

PAGE 1,023

Page = 256/264-bytes

Buffer addressing for the DataFlash standard page size (264-bytes) is referenced in the datasheet using the terminology BFA8 - BFA0 to denote the nine address bits required to designate a byte address within a buffer. Main memory addressing is referenced using the terminology PA9 - PA0 and BA8 - BA0, where PA9 - PA0 denotes the 10-address bits required to designate a page address and BA8 - BA0 denotes the nine address bits required to designate a byte address within the page.

For the “Power of 2” binary page size (256-bytes), the Buffer addressing is referenced in the datasheet using the conventional terminology BFA7 - BFA0 to denote the eight address bits required to designate a byte address within a buffer. Main memory addressing is referenced using the terminology A17 - A0, where A17 - A8 denotes the 10address bits required to designate a page address and A7 - A0 denotes the eight address bits required to designate a byte address within a page.

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4. Read Commands

By specifying the appropriate opcode, data can be read from the main memory or from the SRAM data buffer. The DataFlash supports RapidS protocols for Mode 0 and Mode 3. Please refer to the “Detailed Bit-level Read Timing” diagrams in this datasheet for details on the clock cycle sequences for each mode.

4.1 Continuous Array Read (Legacy Command – E8H): Up to 66MHz

By supplying an initial starting address for the main memory array, the Continuous Array Read command can be utilized to sequentially read a continuous stream of data from the device by simply providing a clock signal; no additional addressing information or control signals need to be provided. The DataFlash incorporates an internal address counter that will automatically increment on every clock cycle, allowing one continuous read operation without the need of additional address sequences. To perform a continuous read from the DataFlash standard page size (264-bytes), an opcode of E8H must be clocked into the device followed by three address bytes (which comprise the 24-bit page and byte address sequence) and four don’t care bytes. The first 10-bits (PA9 - PA0) of the 19-bit address sequence specify which page of the main memory array to read, and the last 9-bits (BA8 - BA0) of the 19-bit address sequence specify the starting byte address within the page. To perform a continuous read from the binary page size (256-bytes), the opcode (E8H) must be clocked into the device followed by three address bytes and four don’t care bytes. The first 10-bits (A17 - A8) of the 18-bits sequence specify which page of the main memory array to read, and the last 8-bits (A7 - A0) of the 18-bits address sequence specify the starting byte address within the page. The don’t care bytes that follow the address bytes are needed to initialize the read operation. Following the don’t care bytes, additional clock pulses on the SCK pin will result in data being output on the SO (serial output) pin.

AT45DB021D

The

CS pin must remain low during the loading of the opcode, the address bytes, the don’t care bytes, 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). When the last bit in the main memory array has been read, the device will continue reading back at the beginning of the first page of memory. As with crossing over page boundaries, no delays will be incurred when wrapping around from the end of the array to the beginning of the array.

A low-to-high transition on the CS pin will terminate the read operation and tri-state the output pin (SO). The maximum SCK frequency allowable for the Continuous Array Read is defined by the f Continuous Array Read bypasses the data buffer and leaves the contents of the buffer unchanged.

4.2 Continuous Array Read (High Frequency Mode – 0BH): Up to 66MHz

This command can be used with the serial interface to read the main memory array sequentially in high speed mode for any clock frequency up to the maximum specified by f page size set to 264-bytes, the CS must first be asserted then an opcode 0BH must be clocked into the device followed by three address bytes and a dummy byte. The first 10-bits (PA9 - PA0) of the 19-bit address sequence specify which page of the main memory array to read, and the last nine bits (BA8 - BA0) of the 19-bit address sequence specify the starting byte address within the page. To perform a continuous read with the page size set to 256-bytes, the opcode, 0BH, must be clocked into the device followed by three address bytes (A17 - A0) and a dummy byte. Following the dummy byte, additional clock pulses on the SCK pin will result in data being output on the SO (serial output) pin.

. To perform a continuous read array with the

CAR1

specification. The

CAR1

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boundaries, no delays will be incurred when wrapping around from the end of the array to the beginning of the array. A low-to-high transition on the CS pin will terminate the read operation and tri-state the output pin (SO). The maximum SCK frequency allowable for the Continuous Array Read is defined by the f Continuous Array Read bypasses the data buffer and leaves the contents of the buffer unchanged.

4.3 Continuous Array Read (Low Frequency Mode: 03H): Up to 33MHz

This command can be used with the serial interface to read the main memory array sequentially without a dummy byte up to maximum frequencies specified by f 264-bytes, the CS must first be asserted then an opcode, 03H, must be clocked into the device followed by three address bytes (which comprise the 24-bit page and byte address sequence). The first 10-bits (PA9 - PA0) of the 19-bit address sequence specify which page of the main memory array to read, and the last nine bits (BA8 - BA0) of the 19-bit address sequence specify the starting byte address within the page. To perform a continuous read with the page size set to 256-bytes, the opcode, 03H, must be clocked into the device followed by three address bytes (A17 - A0). Following the address bytes, additional clock pulses on the SCK pin will result in data being output on the SO (serial output) pin.

The CS pin must remain low during the loading of the opcode, the address bytes, and the reading of data. When the end of a page in the 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). When the last bit in the main memory array has been read, the device will continue reading back at the beginning of the first page of memory. As with crossing over page boundaries, no delays will be incurred when wrapping around from the end of the array to the beginning of the array. A low-to-high transition on the CS pin will terminate the read operation and tri-state the output pin (SO). The Continuous Array Read bypasses the data buffer and leaves the contents of the buffer unchanged.

. To perform a continuous read array with the page size set to

CAR2

specification. The

CAR1

4.4 Main Memory Page Read

A main memory page read allows the user to read data directly from any one of the 2,048-pages in the main memory, bypassing the data buffer and leaving the contents of the buffer unchanged. To start a page read from the DataFlash standard page size (264-bytes), an opcode of D2H must be clocked into the device followed by three address bytes (which comprise the 24-bit page and byte address sequence) and four don’t care bytes. The first 10bits (PA9 - PA0) of the 19-bit address sequence specify the page in main memory to be read, and the last 9-bits (BA8 - BA0) of the 19-bit address sequence specify the starting byte address within that page. To start a page read from the binary page size (256-bytes), the opcode D2H must be clocked into the device followed by three address bytes and four don’t care bytes. The first 10-bits (A17 - A8) of the 18-bit sequence specify which page of the main memory array to read, and the last 8-bits (A7 - A0) of the 18-bit address sequence specify the starting byte address within the page. The don’t care bytes that follow the address bytes are sent to initialize the read operation. Following the don’t care bytes, additional pulses on SCK result in data being output on the SO (serial output) pin. The CS pin must remain low during the loading of the opcode, the address bytes, the don’t care bytes, and the reading of data. When the end of a page in main memory is reached, the device will continue reading back 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 output pin (SO). The maximum SCK frequency allowable for the Main Memory Page Read is defined by the f

specification. The Main Memory Page Read bypasses the data buffer and leaves the contents of the buffer

SCK

unchanged.

4.5 Buffer Read

The SRAM data buffer can be accessed independently from the main memory array, and utilizing the Buffer Read Command allows data to be sequentially read directly from the buffer. Two opcodes, D4H or D1H, can be used for the Buffer Read Command. The use of each opcode depends on the maximum SCK frequency that will be used to

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read data from the buffer. The D4H opcode can be used at any SCK frequency up to the maximum specified by

. The D1H opcode can be used for lower frequency read operations up to the maximum specified by f

CAR1

To perform a buffer read from the DataFlash standard buffer (264-bytes), the opcode must be clocked into the device followed by three address bytes comprised of 15 don’t care bits and 9 buffer address bits (BFA8 - BFA0). To perform a buffer read from the binary buffer (256-bytes), the opcode must be clocked into the device followed by three address bytes comprised of 16 don’t care bits and eight buffer address bits (BFA7 - BFA0). Following the address bytes, one don’t care byte must be clocked in to initialize the read operation. The during the loading of the opcode, the address bytes, the don’t care bytes, 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 output pin (SO).

5. Program and Erase Commands

5.1 Buffer Write

Data can be clocked in from the input pin (SI) into the buffer. To load data into the DataFlash standard buffer (264bytes), a 1-byte opcode, 84H, must be clocked into the device followed by three address bytes comprised of 15 don’t care bits and nine buffer address bits (BFA8 - BFA0). The nine buffer address bits specify the first byte in the buffer to be written. To load data into the binary buffers (256-bytes each), a 1-byte opcode, 84H, must be clocked into the device followed by three address bytes comprised of 16 don’t care bits and eight buffer address bits (BFA7

- BFA0). The eight buffer address bits specify the first byte in the buffer to be written. After the last address byte has been clocked into the device, data can then be clocked in on subsequent clock cycles. If the end of the data buffer is reached, the device will wrap around back to the beginning of the buffer. Data will continue to be loaded into the buffer until a low-to-high transition is detected on the CS pin.

AT45DB021D

CAR2

CS pin must remain low

5.2 Buffer to Main Memory Page Program with Built-in Erase

Data written into the buffer can be programmed into the main memory. A 1-byte opcode, 83H, must be clocked into the device. For the DataFlash standard page size (264-bytes), the opcode must be followed by three address bytes consist of five don’t care bits, 10 page address bits (PA9 - PA0) that specify the page in the main memory to be written and nine don’t care bits. To perform a buffer to main memory page program with built-in erase for the binary page size (256-bytes), the opcode 83H must be clocked into the device followed by three address bytes consisting of six don’t care bits, 10 page address bits (A17 - A8) that specify the page in the main memory to be written and eight don’t care bits. When a low-to-high transition occurs on the CS pin, the part will first erase the selected page in main memory (the erased state is a logic 1) and then program the data stored in the buffer into the specified page in main memory. Both the erase and the programming of the page are internally self-timed and should take place in a maximum time of tEP. During this time, the status register will indicate that the part is busy.

5.3 Buffer to Main Memory Page Program without Built-in Erase

A previously-erased page within main memory can be programmed with the contents of the buffer. A 1-byte opcode, 88H, must be clocked into the device. For the DataFlash standard page size (264-bytes), the opcode must be followed by three address bytes consist of five don’t care bits, 10 page address bits (PA9 - PA0) that specify the page in the main memory to be written and nine don’t care bits. To perform a buffer to main memory page program without built-in erase for the binary page size (256-bytes), the opcode 88H must be clocked into the device followed by three address bytes consisting of six don’t care bits, 10 page address bits (A17 - A8) that specify the page in the main memory to be written and eight don’t care bits. When a low-to-high transition occurs on the CS pin, the part will program the data stored in the buffer into the specified page in the main memory. It is necessary that the page in main memory that is being programmed has been previously erased using one of the erase commands (Page Erase or Block Erase). The programming of the page is internally self-timed and should take place in a maximum time of tP. During this time, the status register will indicate that the part is busy.

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5.4 Page Erase

The Page Erase command can be used to individually erase any page in the main memory array allowing the Buffer to Main Memory Page Program to be utilized at a later time. To perform a page erase in the DataFlash standard page size (264-bytes), an opcode of 81H must be loaded into the device, followed by three address bytes comprised of five don’t care bits, 10 page address bits (PA9 - PA0) that specify the page in the main memory to be erased and nine don’t care bits. To perform a page erase in the binary page size (256-bytes), the opcode 81H must be loaded into the device, followed by three address bytes consist of six don’t care bits, 10 page address bits (A17

- A8) that specify the page in the main memory to be erased and eight don’t care bits. When a low-to-high transition occurs on the internally self-timed and should take place in a maximum time of tPE. During this time, the status register will indicate that the part is busy.

5.5 Block Erase

A block of eight pages can be erased at one time. This command is useful when large amounts of data has to be written into the device. This will avoid using multiple Page Erase Commands. To perform a block erase for the DataFlash standard page size (264-bytes), an opcode of 50H must be loaded into the device, followed by three address bytes comprised of five don’t care bits, seven page address bits (PA9 -PA3) and 12 don’t care bits. The seven page address bits are used to specify which block of eight pages is to be erased. To perform a block erase for the binary page size (256-bytes), the opcode 50H must be loaded into the device, followed by three address bytes consisting of six don’t care bits, seven page address bits (A17 - A11) and 11 don’t care bits. The 9-page address bits are used to specify which block of eight pages is to be erased. When a low-to-high transition occurs on the CS pin, the part will erase the selected block of eight pages. The erase operation is internally self-timed and should take place in a maximum time of tBE. During this time, the status register will indicate that the part is busy.

CS pin, the part will erase the selected page (the erased state is a logical 1). The erase operation is

Table 5-1. Block Erase Addressing

PA9/

A17

0000000XXX0

0000001XXX1

0000010XXX2

0000011XXX3

•

1111100XXX124

1111101XXX125

1111110XXX126

1111111XXX127

PA8/

A16

5.6 Sector Erase

The Sector Erase command can be used to individually erase any sector in the main memory. There are four sectors and only one sector can be erased at one time. To perform sector 0a or sector 0b erase for the DataFlash standard page size (264-bytes), an opcode of 7CH must be loaded into the device, followed by three address bytes comprised of five don’t care bits, seven page address bits (PA9 - PA3) and 12 don’t care bits. To perform a sector 1-7 erase, the opcode 7CH must be loaded into the device, followed by three address bytes comprised of five don’t care bits, three page address bits (PA9 - PA7) and 16 don’t care bits. To perform sector 0a or sector 0b erase for

PA7/

A15

•

PA6/

A14

•

PA5/

A13

•

PA4/

A12

•

PA3/

A11

•

PA2/

A10

•

PA1/

•

PA0/

A8 Block

•

AT45DB021D

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AT45DB021D

the binary page size (25-bytes), an opcode of 7CH must be loaded into the device, followed by three address bytes comprised of six don’t care bits and seven page address bits (A17 - A11) and 11 don’t care bits. To perform a sector 1-seven erase, the opcode 7CH must be loaded into the device, followed by three address bytes comprised of six don’t care bit and three page address bits (A17 - A15) and 16 don’t care bits. The page address bits are used to specify any valid address location within the sector which is to be erased. When a low-to-high transition occurs on the CS pin, the part will erase the selected sector. The erase operation is internally self-timed and should take place in a maximum time of tSE. During this time, the status register will indicate that the part is busy.

Table 5-2. Sector Erase Addressing

PA9/

A17

0000000XXX0a

0000001XXX0b

•

01 1 XXXXXXX5

10 0 XXXXXXX6

11 1 XXXXXXX7

5.7 Chip Erase

The entire main memory can be erased at one time by using the Chip Erase command.

To execute the Chip Erase command, a 4-byte command sequence C7H, 94H, 80H and 9AH must be clocked into the device. Since the entire memory array is to be erased, no address bytes need to be clocked into the device, and any data clocked in after the opcode will be ignored. After the last bit of the opcode sequence has been clocked in, the CS pin can be deasserted to start the erase process. The erase operation is internally self-timed and should take place in a time of tCE. During this time, the Status Register will indicate that the device is busy.

The Chip Erase command will not affect sectors that are protected or locked down; the contents of those sectors will remain unchanged. Only those sectors that are not protected or locked down will be erased.

PA8/

A16

•

PA7/

A15

•

PA6/

A14

•

PA5/

A13

•

PA4/

A12

•

PA3/

A11

•

PA2/

A10

•

PA1/

•

PA0/

A8 Sector

•

The WP pin can be asserted while the device is erasing, but protection will not be activated until the internal erase cycle completes.

Table 5-3. Chip Erase Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Chip Erase C7H 94H 80H 9AH

Figure 5-1. Chip Erase

3638K–DFLASH–11/2012

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

5.8 Main Memory Page Program Through Buffer

This operation is a combination of the Buffer Write and Buffer to Main Memory Page Program with Built-in Erase operations. Data is first clocked into the buffer from the input pin (SI) and then programmed into a specified page in the main memory. To perform a main memory page program through buffer for the DataFlash standard page size (264-bytes), a 1-byte opcode, 82H, must first be clocked into the device, followed by three address bytes. The address bytes are comprised of five don’t care bits, 10 page address bits, (PA9 - PA0) that select the page in the main memory where data is to be written, and nine buffer address bits (BFA8 - BFA0) that select the first byte in the buffer to be written. To perform a main memory page program through buffer for the binary page size (256bytes), the opcode 82H must be clocked into the device followed by three address bytes consisting of six don’t care bits, 10 page address bits (A17 - A8) that specify the page in the main memory to be written, and eight buffer address bits (BFA7 - BFA0) that selects the first byte in the buffer to be written. After all address bytes are clocked in, the part will take data from the input pins and store it in the specified data buffer. If the end of the buffer is reached, the device will wrap around back to the beginning of the buffer. When there is a low-to-high transition on the CS pin, the part will first erase the selected page in main memory to all ones and then program the data stored in the buffer into that memory page. Both the erase and the programming of the page are internally self-timed and should take place in a maximum time of t

. During this time, the status register will indicate that the part is busy.

6. Sector Protection

Two protection methods, hardware and software controlled, are provided for protection against inadvertent or erroneous program and erase cycles. The software controlled method relies on the use of software commands to enable and disable sector protection while the hardware controlled method employs the use of the Write Protect (WP) pin. The selection of which sectors that are to be protected or unprotected against program and erase operations is specified in the nonvolatile Sector Protection Register. The status of whether or not sector protection has been enabled or disabled by either the software or the hardware controlled methods can be determined by checking the Status Register.

6.1 Software Sector Protection

6.1.1 Enable Sector Protection Command

Sectors specified for protection in the Sector Protection Register can be protected from program and erase operations by issuing the Enable Sector Protection command. To enable the sector protection using the software controlled method, the CS pin must first be asserted as it would be with any other command. Once the CS pin has been asserted, the appropriate 4-byte command sequence must be clocked in via the input pin (SI). After the last bit of the command sequence has been clocked in, the CS pin must be deasserted after which the sector protection will be enabled.

Table 6-1. Enable Sector Protection Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Enable Sector Protection 3DH 2AH 7FH A9H

Figure 6-1. Enable Sector Protection

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

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6.1.2 Disable Sector Protection Command

To disable the sector protection using the software controlled method, the be with any other command. Once the Sector Protection command must be clocked in via the input pin (SI). After the last bit of the command sequence has been clocked in, the

CS pin must be deasserted after which the sector protection will be disabled. The WP pin

must be in the deasserted state; otherwise, the Disable Sector Protection command will be ignored.

Table 6-2. Disenable Sector Protection Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Disable Sector Protection 3DH 2AH 7FH 9AH

Figure 6-2. Disable Sector Protection

AT45DB021D

CS pin must first be asserted as it would

CS pin has been asserted, the appropriate 4-byte sequence for the Disable

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

6.1.3 Various Aspects About Software Controlled Protection

Software controlled protection is useful in applications in which the processor. In such instances, the WP pin may be left floating (the WP pin is internally pulled high) and sector protection can be controlled using the Enable Sector Protection and Disable Sector Protection commands.

If the device is power cycled, then the software controlled protection will be disabled. Once the device is powered up, the Enable Sector Protection command should be reissued if sector protection is desired and if the WP pin is not used.

7. Hardware Controlled Protection

Sectors specified for protection in the Sector Protection Register and the Sector Protection Register itself can be protected from program and erase operations by asserting the WP pin and keeping the pin in its asserted state. The Sector Protection Register and any sector specified for protection cannot be erased or reprogrammed as long as the WP pin is asserted. In order to modify the Sector Protection Register, the WP pin must be deasserted. If the WP pin is permanently connected to GND, then the content of the Sector Protection Register cannot be changed. If the WP pin is deasserted, or permanently connected to VCC, then the content of the Sector Protection Register can be modified.

WP pin is not or cannot be controlled by a host

The WP pin will override the software controlled protection 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 would enable the sector protection within the maximum specified t deasserted; however, the sector protection would no longer be enabled (after the maximum specified t 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 sector 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 Sector Protection command is also ignored whenever the WP pin is asserted.

A noise filter is incorporated to help protect against spurious noise that may inadvertently assert or deassert the WP pin.

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time. When the WPpinis

WPE

WPD

time) as

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.

Figure 7-1.

WP Pin and Protection Status

Table 7-1.

Time

Period

1 High

2 Low X X Enabled Read Only

3 High

WP Pin and Protection Status

Enable Sector Protection

WP Pin

Command Not Issued Previously

Issue Command

Command Issued During Period 1

Issue Command

7.1 Sector Protection Register

The nonvolatile Sector Protection Register specifies which sectors are to be protected or unprotected with either the software or hardware controlled protection methods. The Sector Protection Register contains 8-bytes of data, of which byte locations zero through seven contain values that specify whether sectors zero through seven will be protected or unprotected. The Sector Protection Register is user modifiable and must first be erased before it can be reprogrammed. Table 7-3 illustrates the format of the Sector Protection Register

Command

–

or 2

–

Disable Sector

Protection Command

Issue Command

–

Not Issued Yet

Issue Command

–

Sector

Protection Status

Disabled Disabled

Enabled

Disabled

Enabled

Sector

Protection

Read/Write Read/Write Read/Write

Table 7-2. Sector Protection Register.

Sector Number 0 (0a, 0b) 1 to 7

Protected

See Table 7-3

Unprotected 00H

FFH

Table 7-3. Sector 0 (0a, 0b)

0a 0b

(Page 0-7) (Page 8-127)

Bit7,6 Bit5,4 Bit1,0

Sectors 0a, 0b Unprotected 00 00 xx xx 0xH

Protect Sector 0a 11 00 xx xx CxH

Protect Sector 0b (Page 8-127) 00 11 xx xx 3xH

Protect Sectors 0a (Page 0-7), 0b (Page 8-127)

Note: 1. The default value for bytes 0 through 7 when shipped from Adesto is 00H

x = don’t care

(1)

11 11 xx xx FxH

Bit3,2

Value

Data

AT45DB021D

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7.1.1 Erase Sector Protection Register Command

In order to modify and change the values of the Sector Protection Register, it must first be erased using the Erase Sector Protection Register command.

AT45DB021D

To erase the Sector Protection Register, the

CS pin must first be asserted as it would be with any other command. Once the CS pin has been asserted, the appropriate 4-byte opcode sequence must be clocked into the device via the SI pin. The 4-byte opcode sequence must start with 3DH and be followed by 2AH, 7FH, and CFH. After the last bit of the opcode sequence has been clocked in, the CS pin must be deasserted to initiate the internally self-timed erase cycle. The erasing of the Sector Protection Register should take place in a time of t

, during which time the

Status Register will indicate that the device is busy. If the device is powered-down before the completion of the erase cycle, then the contents of the Sector Protection Register cannot be guaranteed.

The Sector Protection Register can be erased with the sector protection enabled or disabled. Since the erased state (FFH) of each byte in the Sector Protection Register is used to indicate that a sector is specified for protection, leaving the sector protection enabled during the erasing of the register allows the protection scheme to be more effective in the prevention of accidental programming or erasing of the device. If for some reason an erroneous program or erase command is sent to the device immediately after erasing the Sector Protection Register and before the register can be reprogrammed, then the erroneous program or erase command will not be processed because all sectors would be protected.

Table 7-4. Erase Sector Protection Register Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Erase Sector Protection Register 3DH 2AH 7FH CFH

Figure 7-2. Erase Sector Protection Register

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

7.1.2 Program Sector Protection Register Command

Once the Sector Protection Register has been erased, it can be reprogrammed using the Program Sector Protection Register command.

To program the Sector Protection Register, the CS pin must first be asserted and the appropriate 4-byte opcode sequence must be clocked into the device via the SI pin. The 4-byte opcode sequence must start with 3DH and be followed by 2AH, 7FH, and FCH. After the last bit of the opcode sequence has been clocked into the device, the data for the contents of the Sector Protection Register must be clocked in. As described in Section 7.1, the Sector Protection Register contains 4-bytes of data, so 4-bytes must be clocked into the device. The first byte of data corresponds to sector zero, the second byte corresponds to sector one, the third byte corresponds to sector two, and the last byte of data corresponding to sector three.

After the last data byte has been clocked in, the CS pin must be deasserted to initiate the internally self-timed program cycle. The programming of the Sector Protection Register should take place in a time of tP, during which time the Status Register will indicate that the device is busy. If the device is powered-down during the program cycle, then the contents of the Sector Protection Register cannot be guaranteed.

IfthepropernumberofdatabytesisnotclockedinbeforetheCS pin is deasserted, then the protection status of the sectors corresponding to the bytes not clocked in can not be guaranteed. For example, if only the first two bytes are clocked in instead of the complete 8-bytes, then the protection status of the last six sectors cannot be

Opcode

Byte 4

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guaranteed. Furthermore, if more than 8-bytes of data is clocked into the device, then the data will wrap back around to the beginning of the register. For instance, if 9-bytes of data are clocked in, then the ninth byte will be stored at byte location zero of the Sector Protection Register.

If a value other than 00H or FFH is clocked into a byte location of the Sector Protection Register, then the protection status of the sector corresponding to that byte location cannot be guaranteed. For example, if a value of 17H is clocked into byte location two of the Sector Protection Register, then the protection status of sector two cannot be guaranteed.

The Sector Protection Register can be reprogrammed while the sector protection enabled or disabled. Being able to reprogram the Sector Protection Register with the sector protection enabled allows the user to temporarily disable the sector protection to an individual sector rather than disabling sector protection completely.

The Program Sector Protection Register command utilizes the internal SRAM buffer for processing. Therefore, the contents of the buffer will be altered from its previous state when this command is issued.

Table 7-5. Program Sector Protection Register Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Program Sector Protection Register 3DH 2AH 7FH FCH

Figure 7-3. Program Sector Protection Register

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

7.1.3 Read Sector Protection Register Command

To read the Sector Protection Register, the CS pin must first be asserted. Once the CS pin has been asserted, an opcode of 32H and three dummy bytes must be clocked in via the SI pin. After the last bit of the opcode and dummy bytes have been clocked in, any additional clock pulses on the SCK pins will result in data for the content of the Sector Protection Register being output on the SO pin. The first byte corresponds to sector 0 (0a, 0b), the second byte corresponds to sector one, the third byte corresponds to sector two, and the last byte (byte four) corresponds to sector three. Once the last byte of the Sector Protection Register has been clocked out, any additional clock pulses will result in undefined data being output on the SO pin. The CS must be deasserted to terminate the Read Sector Protection Register operation and put the output into a high-impedance state.

Table 7-6. Read Sector Protection Register Command

Command Byte 1 Byte 2 Byte 3 Byte 4

Read Sector Protection Register 32H xxH xxH xxH

Note: xx = Dummy Byte

Figure 7-4. Read Sector Protection Register

Opcode

Byte 4

Data Byte

n + 1

Data Byte

n + 3

Opcode X X X

Each transition represents 8 bits

AT45DB021D

Data BytenData Byte

n + 1

Data Byte

n + 3

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7.1.4 Various Aspects About the Sector Protection Register

The Sector Protection Register is subject to a limit of 10,000 erase/program cycles. Users are encouraged to carefully evaluate the number of times the Sector Protection Register will be modified during the course of the applications’ life cycle. If the application requires that the Sector Protection Register be modified more than the specified limit of 10,000 cycles because the application needs to temporarily unprotect individual sectors (sector protection remains enabled while the Sector Protection Register is reprogrammed), then the application will need to limit this practice. Instead, a combination of temporarily unprotecting individual sectors along with disabling sector protection completely will need to be implemented by the application to ensure that the limit of 10,000 cycles is not exceeded.

8. Security Features

8.1 Sector Lockdown

The device incorporates a Sector Lockdown mechanism that allows each individual sector to be permanently locked so that it becomes read only. This is useful for applications that require the ability to permanently protect a number of sectors against malicious attempts at altering program code or security information. Once a sector is

locked down, it can never be erased or programmed, and it can never be unlocked.

To issue the Sector Lockdown command, the CS pin must first be asserted as it would be for any other command. Once the CS pin has been asserted, the appropriate 4-byte opcode sequence must be clocked into the device in the correct order. The 4-byte opcode sequence must start with 3DH and be followed by 2AH, 7FH, and 30H. After the last byte of the command sequence has been clocked in, then three address bytes specifying any address within the sector to be locked down must be clocked into the device. After the last address bit has been clocked in, the CS pin must then be deasserted to initiate the internally self-timed lockdown sequence.

AT45DB021D

The lockdown sequence should take place in a maximum time of tP, during which time the Status Register will indicate that the device is busy. If the device is powered-down before the completion of the lockdown sequence, then the lockdown status of the sector cannot be guaranteed. In this case, it is recommended that the user read the Sector Lockdown Register to determine the status of the appropriate sector lockdown bits or bytes and reissue the Sector Lockdown command if necessary.

Table 8-1. Sector Lockdown

Command Byte 1 Byte 2 Byte 3 Byte 4

Sector Lockdown 3DH 2AH 7FH 30H

Figure 8-1. Sector Lockdown

Opcode

Byte 1

Each transition represents 8 bits

Opcode

Byte 2

Opcode

Byte 3

Opcode

Byte 4

Address

Bytes

Address

Bytes

Address

Bytes

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