Note that the chip on the Arduino board contains an internal EEPROM, so follow this tutorial only if you need more space than it provides. Serial Peripheral Interface SPI is a synchronous serial data protocol used by Microcontrollers for communicating with one or more peripheral devices quickly over short distances. It can also be used for communication between two microcontrollers. With an SPI connection there is always one master device usually a microcontroller which controls the peripheral devices.
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Dt Sheet. Clock Frequency Temp. Ranges 25AA 1. Access to the device is controlled through a Chip Select CS input. While the device is paused, transitions on its inputs will be ignored, with the exception of Chip Select, allowing the host to service higher priority interrupts. This is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. Exposure to maximum rating conditions for an extended period of time may affect device reliability.
Units Conditions 2. TABLE 2. During a read cycle, data is shifted out on this pin after the falling edge of the serial clock. A high level deselects the device and forces it into Standby mode.
However, a programming cycle which is already initiated or in progress will be completed, regardless of the CS input signal. If CS is brought high during a program cycle, the device will go into Standby mode as soon as the programming cycle is complete.
When the device is deselected, SO goes to the high-impedance state, allowing multiple parts to share the same SPI bus. A low-to-high transition on CS after a valid write sequence initiates an internal write cycle. After powerup, a low level on CS is required prior to any sequence being initiated.
All other operations function normally. When WP is high, all functions, including writes to the nonvolatile bits in the Status register operate normally. If an internal write cycle has already begun, WP going low will have no effect on the write.
This allows the user to install the 25XX in a system with WP pin grounded and still be able to write to the Status register. It receives instructions, addresses, and data. Data is latched on the rising edge of the serial clock. Instructions, addresses, or data present on the SI pin are latched on the rising edge of the clock input, while data on the SO pin is updated after the falling edge of the clock input.
It must be held high any time this function is not being used. Once the device is selected and a serial sequence is underway, the HOLD pin may be pulled low to pause further serial communication without resetting the serial sequence. The 25XX must remain selected during this sequence. The SI, SCK, and SO pins are in a high-impedance state during the time the device is paused and transitions on these pins will be ignored.
This is done by setting CS low and then clocking out the proper instruction into the 25XX After all eight bits of the instruction are transmitted, the CS must be brought high to set the write enable latch.
If the write operation is initiated immediately after the WREN instruction without CS being brought high, the data will not be written to the array because the write enable latch will not have been properly set. The 25XX contains an 8-bit instruction register. Table contains a list of the possible instruction bytes and format for device operation.
After the correct READ instruction and address are sent, the data stored in the memory at the selected address is shifted out on the SO pin.
The data stored in the memory at the next address can be read sequentially by continuing to provide clock pulses. The internal address pointer is automatically incremented to the next higher address after each byte of data is shifted out.
When the highest address is reached 0FFFh , the address counter rolls over to address h allowing the read cycle to be continued indefinitely. The read operation is terminated by raising the CS pin Figure Up to 32 bytes of data can be sent to the 25XX before a write cycle is necessary.
The only restriction is that all of the bytes must reside in the same page. A page address begins with xxxx xxxx xxx0 and ends with xxxx xxxx xxx1 If the internal address counter reaches xxxx xxxx xxx1 and the clock continues, the counter will roll back to the first address of the page and overwrite any data in the page that may have been written. For the data to be actually written to the array, the CS must be brought high after the least significant bit D0 of the nth data byte has been clocked in.
If CS is brought high at any other time, the write operation will not be completed. Refer to Figure and Figure for more detailed illustrations on the byte write sequence and the page write sequence respectively.
A read attempt of a memory array location will not be possible during a write cycle. When the write cycle is completed, the write enable latch is reset.
This latch must be set before any write operation will be completed internally. This bit is read-only. The Status register may be read at any time, even during a write cycle.
These bits are set by the user issuing the WRSR instruction. These bits are nonvolatile. The Write Status Register instruction WRSR allows the user to select one of four levels of protection for the array by writing to the appropriate bits in the Status register. The array is divided up into four segments.
The user has the ability to write-protect none, one, two, or all four of the segments of the array. The partitioning is controlled as shown in Table Standard marking consists of Microchip part number, year code, week code, and traceability code.
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25LC320 32K2.5VSPIBusSerialEEPROM. Datasheet pdf. Equivalent
RS Stock No. Product Details. Maximum Operating Temperature. Minimum Operating Supply Voltage.
Microchip 25LC320-I/SN, 32kbit Serial EEPROM Memory, 230ns 8-Pin SOIC SPI
The Microchip Technology Inc. Interface SPI compatible serial bus. The bus signals. SI and data out SO lines. Access to the device is. There are two other inputs that provide the end user. Communication to the device.
Interfacing a Serial EEPROM Using SPI