EMIFA Minimum Operating Frequency

You can reduce the clock rate of the EMIFA by slowing down PLL0.SYSCLK3 (see "Changing the SYSCLK Dividers" in the System Reference guide for the L138, SPRUGM7).  However, this will increase the access time (reduce the clock rate) to all the peripherals and/or memory you have connected to EMIFA.  A better method would be to program the setup, strobe, and hold timings for each EMA_CS pin on the EMIFA to get the desired access time (access time = setup + strobe + hold).  This is assuming that you are 1. using async mode for the EMIFA, and 2. that you have used a different EMA_CS pin for each of your peripherals.  The advantage of this method is that you use a faster access time for faster peripherals, and a slower access time for slower peripherals.  If you are using the SDRAM mode of the EMIFA, then you have to change the SYSCLK frequency.