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AN302 - F-RAM™ SPI Read and Write Internal Operation and Data Protection | 赛普拉斯半导体

AN302 - F-RAM™ SPI Read and Write Internal Operation and Data Protection

2020 年 5 月 30 日
This is an Obsolete Application Note
The document AN302 - F-RAM™ SPI Read and Write Internal Operation and Data Protection has been marked as obsolete. The obsolete version of this application note is still available with the below description but may not be complete or valid any longer. If you have any questions or require support in regards to the below application note content, please click here and create a technical support case.
F-RAM SPI devices have no power management circuits other than a simple internal power-on reset circuit. The system designer must ensure that VDD, VDD power up ramp rate, and VDD power down ramp rate are within datasheet tolerances to prevent any incorrect operation. The system designer should be aware of chip enable and VDD states during power cycles, especially considering the strange waveforms delivered by switching power supplies, manually controlled power switches, multi-stage turn-on supplies, and so on. As mentioned later in this document, the control pin (("CS" ) ̅) must be held inactive (HIGH) during any power transition. This application note offers system design suggestions for keeping the ("CS" ) ̅ pin HIGH during power transitions to avoid data corruption. It also describes the internal read and write operations of Cypress's high-speed F-RAM SPI devices. For more details on SPI F-RAM, refer to AN304 SPI Guide for F-RAM.

AN302 discusses the importance of keeping HIGH during power transitions and suggests a circuit to accomplish this. It also describes the internal operation of Cypress's high-speed SPI F-RAM devices during memory read & write operations


Ferroelectric random access memory (F-RAM) is a nonvolatile memory that uses a ferroelectric technology for storing data. The SPI F-RAM scores over other nonvolatile serial memory options due to its fast write speed and endurance (the number of writes that can be done before damaging the F-RAM’s nonvolatile cells). Hundreds of bytes can be written in tens of microseconds. EEPROM and flash memories require tens of milliseconds to do the same. Writing data quickly before losing power is particularly useful in systems that require preserving machine state information, parameter settings, or other vital data in a power-down event. To preserve data make certain to control signals at both power up and power down.