and more. Having a good, optimized and easy-to-use software driver is as important as a well designed and fast device. This is why we have developed and are now offering an optimized F-RAM driver for one of the industry's most popular microcontroller platforms: STM32. The latest STM32 SPI controller (OctoSPI) supports various SPI modes including x1, x4 and x8 width, SDR and DDR protocols as well as fully memory mapped access for both read and write operations.
Thanks to an advanced prefetching mechanism, the performance that can be achieved on these platforms is close to the theoretical maximum bus bandwidth (> 90%). Quad SPI (QPI) DDR mode F-RAM access is so fast that an Excelon QSPI F-RAM device can even be used as frame buffer. At SPI clock speeds of 17.5 MHz and higher it is fast enough to support the required read bandwidth of a STM32H7B3 Discovery Kit display controller/TFT. At 46.7 MHz it offers enough headroom to mix the traffic with concurrent frame buffer updates (write operations).
The following picture shows the snapshot of a graphical notepad application with a persistent frame buffer that is implemented via F-RAM. After a power loss (due to an emergency situation or on purpose), the old image is still fully available so that the application can be instantly and seamlessly resumed.
Of course, Cypress F-RAM can also be used for other purposes such as data logging or to make critical application data and variables persistent. In all cases, it provides instant writes (no data loss), infinite endurance as well as long retention.
The new Excelon F-RAM driver can be downloaded from Cypress' F-RAM github (in the STM32 directory).