2.2.2. SDRAM interaction with frequency and power modes

The SDRAM refresh period is programmed into the MPMC in HCLK tick units. This setting must be reprogrammed when the operating frequency of the ARM926PXP development chip changes (when the PLL frequency control is altered or if the system switched operating mode between NORMAL or SLOW). When moving to:

Before entering operating modes where the HCLK frequency is very low or stalled (DOZE and SLEEP modes) the SDRAM must be put into self-refresh mode. In this mode the SDRAM is not accessible.

Note

Other peripherals, such as the SCI, must have the correct shutdown sequence applied before the system can be put into the DOZE or SLEEP mode.

Note

The feedback clock to the MPMC and SSMC are input to the clock selection and gating block shown in Figure 2.4. MPMCFBCLK[3:0] and SMFBCLK[3:0] are only buffered in this block.

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