Using C to interface Texas Instruments' MSP430XXXX MCUs with SPI serial EEPROMs

The 25XXX series serial EEPROMs from Microchip Technology support a half-duplex SPI protocol. The bus is controlled by the microcontroller (master), which accesses the 25XXX serial EEPROM (slave). The bus signals required consist of a clock input plus separate data in and data out lines. Access to the 25XXX serial EEPROM is controlled through a Chip Select (CS) input. Maximum clock frequencies range from 3MHz to 20MHz. Communication to the 25XXX serial EEPROM can be paused via the hold pin (HOLD). While the EEPROM is paused, transitions on its inputs are ignored, except for the CS, allowing the MCU to service higher priority interrupts. After releasing the HOLD pin, the operations resume from the point when the hold was asserted.

The main features of the 25XXX serial EEPROMs are:

??SPI-compatible serial interface bus
??EEPROM densities range from 1Kbit to 1Mbit
??Bus speed from 3MHz to 20MHz
??Voltage range from 1.8V to 5.5V
??Low-power operation
??Temperature range from -40°C to +125°C
??Over 1,000,000 erase/write cycles
??Built-in write protection.

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