Please confirm the following.
1. Please confirm whether the pin used in SDRAM is selected by the pin function controller(PFC). There are some from which the SDRAM interface of SH7206 is allocated to two or more pins.
2. Please confirm the setting of AC characteristic switching register (ACSWR).
It is necessary to set ACSWR when using it in clock mode 2.
3. Please confirm whether SDMR (synchronous DRAM mode register) is correctly set.
4. Please confirm whether interval of the SDRAM refreshing cycle set by RTCSR (refreshing timer/control register) and RTCOR (refreshing time constant register) fulfills the specified value of SDRAM.
5. Please confirm whether the setup time and the holding time of each signal of SDRAM are fulfilled.