SPRUIE9D May 2017 – May 2024 DRA74P , DRA75P , DRA76P , DRA77P
The EMIF supports SDRAM power-down mode for low power. The EMIF automatically puts the SDRAM into power-down mode after it is idle for EMIF_POWER_MANAGEMENT_CONTROL[15:12] PD_TIM number of DDR clock cycles and the EMIF_POWER_MANAGEMENT_CONTROL[10:8] LP_MODE bit field is set to 0x4. In power-down mode, the EMIF does not stop the clocks to the SDRAM. The EMIF maintains CKE pin low to maintain the power-down mode.
If refresh-must level is not reached before power-down entering, EMIF will not precharge all SDRAM banks before it issues the power-down command. As a result of this EMIF puts the SDRAM in active power-down mode. If refresh-must level is reached before power-down entering, EMIF will precharge all SDRAM banks and before it issues the power-down command, EMIF issues refreshes until refresh-release level is reached. As a result of this EMIF puts the SDRAM in precharge power-down mode.
When the SDRAM is in power-down mode, the EMIF services register accesses normally.
If the SDRAM is in power-down mode and one of the following occurs, the EMIF brings SDRAM out of power-down mode:
If refresh-must level brings the SDRAM out of power-down mode, EMIF puts it in power-down again when the refreshes are complete and keeps this state until the next SDRAM request.
To exit power-down, the EMIF: