Extend memories by using external high speed memories interfaced to Quad-SPI modules on STM32 micros, app note from STMicroelectronics. Link here (PDF)
This application note describes the Quad-SPI interface on the STM32 microcontrollers and explains how to use the module to configure, program, and read external Quad-SPI memories. It describes some typical use cases to use Quad-SPI interface based on some software examples from the STM32Cube firmware package and from the STM32F7 application notes.
from Dangerous Prototypes http://bit.ly/2rSciid