SPRUHX5I August 2014 – May 2024 TMS320F28374S , TMS320F28375S , TMS320F28375S-Q1 , TMS320F28376S , TMS320F28377S , TMS320F28377S-Q1 , TMS320F28378S , TMS320F28379S
The EMIF can be programmed to enter the self-refresh state by setting the SR bit of SDRAM_CR to 1. This causes the EMIF to issue the SLFR command after completing any outstanding SDRAM access requests and clearing the refresh backlog counter by performing one or more auto refresh cycles. This places the attached SDRAM device into self-refresh mode in which the EMIF consumes a minimal amount of power while performing the refresh cycles.
While in the self-refresh state, the EMIF continues to service asynchronous bank requests and register accesses as normal, with one caveat. The EMIF does not park the data bus following a read to asynchronous memory while in the self-refresh state. Instead, the EMIF tri-states the data bus. Therefore, it is not recommended to perform asynchronous read operations while the EMIF is in the self-refresh state to prevent floating inputs on the data bus. More information about data bus parking can be found in Section 24.2.7.
The EMIF exits from the self-refresh state, if either of the following events occur:
The EMIF exits from the self-refresh state by driving EM1SDCKE high and performing an auto refresh cycle.
The attached SDRAM device must also be placed into self-refresh mode when changing the frequency of EM1CLK. If the frequency of EM1CLK changes while the SDRAM is not in self-refresh mode, Procedure B in Section 24.2.5.5 must be followed to reinitialize the device.