Cypress offers a comprehensive portfolio of ferroelectric RAM nonvolatile memory products that instantly capture and store critical data in the event of power outages. In mission-critical data recording applications, such as high-performance programmable logic controllers (PLCs) on factory floors that require high reliability control and throughput, or life-enhancing patient monitoring devices implanted in the human body designed with low power consumption, small sizes of memory, the Cyrus FRAM provides instant nonvolatility and almost unlimited durability, Without affecting speed or energy efficiency. This paper introduces the 64Kbit nonvolatile ferroelectric memory FM25640B.

The FM25640B is a 64Kbit non-volatile ferroelectric memory using advanced ferroelectric technology. Ferroelectric random access memory, or FRAM, is nonvolatile and performs reads and writes similar to RAM. It provides 151 years of reliable data retention while eliminating the complexity, overhead, and system-level reliability issues caused by serial flash, EEPROM, and other non-volatile memory.

Unlike serial flash and EEPROM, the FM25640B performs write operations at bus speed. There is no write delay. As soon as each byte is successfully transferred to the device, the data is written to the memory array. Start the next bus cycle without data polling. In addition, the product provides considerable write durability compared to other non-volatile memory. The FM25640B can support 1014 read/write cycles, or 100 million times more write cycles than the EEPROM.

These features make the FM25640B ideal for nonvolatile memory applications that require frequent or rapid writes. Examples range from data collection, where the number of write cycles can be critical, to demanding industrial controls, where long write times on serial flash or EEPROM can result in data loss.

The FM25640B offers great benefits to users of serial EEPROM or flash memory as a hardware replacement. FM25640B adopts high speed SPI bus, which enhances the high speed write ability of FRAM technology. Device specifications are guaranteed in the industrial temperature range of — 40℃ to +85℃.

■ 64-kbit Ferram (❐), logic organized with 8K×8 ❐, 100 trillion (1014) read/write ❐, 151-year ❐, NoDelay™ written ❐. Advanced, highly reliable Ferram technology ■ Very fast SerialPeripherialInterface (SPI) ❐ With 20MHz serial flash and EEPROM direct hardware replaceable ❐ With SPI mode 0(0,0) and mode 3(1,1) □ fully written ❐ with hardware protected with WP pin ❐ With software protected with write disable❐ With 1/4, 1/2, or the entire class of software blocks protected ■ Low-power ❐250μA1MHz active current ❐4μA (Typical) STAND-by current ■ Voltage operation: VDD=4.5V to 5.5V ■ Industrial temperature: — 40 ° C to +85 ° C ■ 8-pin small shape integrated circuit (SOIC) ❐ ■ RoHS compliant

The FM25640B is a serial RAM memory. The memory array is logically organized into 8K×8 bits and is accessed using an industry-standard Serial Peripheral Interface (SPI) bus. The functional operation of a FRM is similar to that of serial flash memory and serial EEPROM. The main difference between the FM25640B and a serial flash memory or EEPROM with the same pin arrangement is the excellent write performance, high durability, and low power consumption of the FRAM.

When the memory architecture accesses the FM25640B, the user addresses 8K locations, each with 8 data bits. The eight data bits are moved in and out in sequence. These addresses are accessed using the SPI protocol, which includes chip selection (allowing multiple devices on the bus), opcodes, and two-byte addresses. The upper three bits of the address range are “irrelevant” values. The 13-bit full address uniquely specifies the address of each byte.

Most functions of the FM25640B are either controlled by the SPI interface or handled by the onboard circuitry. The access time for the memory operation is essentially zero, exceeding the time required for the serial protocol. That is, read or write memory at the speed of the SPI bus. Unlike serial flash or EEPROM, because writing occurs at bus speed, there is no need to poll the device to see if it is ready. The write operation is complete when a new bus transaction can be transferred to the device. This is explained in more detail in the Interfaces section.

The FM25640B does not contain any power management circuit except for a simple internal power-on reset circuit. It is the user’s responsibility to ensure that the VDD is within the data table tolerance to prevent erroneous operations. It is not recommended to turn off the device while the chip is enabled.

Serial Peripheral Interface -SPI Bus FM25640B is an SPI slave device, running at speeds up to 20MHz. This high-speed serial bus provides high-performance serial communication for SPI master devices. Many common microcontrollers have hardware SPI ports that allow direct interfaces. For microcontrollers that don’t have them, it’s easy to emulate ports with plain port pins.