/**
  **************************************************************************
  * @file     readme.txt
  * @version  v2.0.0
  * @date     2021-11-26
  * @brief    readme
  **************************************************************************
  */

  this demo is based on the at-start board, in this demo, the code contains
  two project targets. please follow below steps to test.
  - step 1:
  rebuild all target files.
  - step 2:
  select target "set_sram_xxk", download. if everything is ok, the led4 will
  turn on.

  this demo call function extend_sram() when startup.
  for details, please refer to the application note document AN0026.
