CLKSTOP_REQ
CLKSTOP_ACK
LRST
EMIFA PSC
PLL
VCLKSTOP_REQ
VCLKSTOP_ACK
MOD_G_RST
VCLK
CHIP_RST
EMIFA
Memory
Controller
PLL_SYSCLK
Architecture
874
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
External Memory Interface A (EMIFA)
19.2.14 Power Management
Power dissipation from the EMIFA memory controller may be managed by following methods:
•
Self-refresh mode
•
Power-down mode
•
Gating input clocks to the module off
Gating input clocks off to the EMIFA memory controller achieves higher power savings when compared to
the power savings of self-refresh or power down mode. The input clocks are turned off outside of the
EMIFA memory controller through the use of the Power and Sleep Controller (PSC) and the PLL
controller.
shows the connections between the EMIFA memory controller, PSC, and PLL.
Before gating clocks off, the EMIFA memory controller must place the SDR SDRAM memory in self-
refresh mode. If the external memory requires a continuous clock, the clock provided by the PLL must not
be turned off because this may result in data corruption. See the following subsections for the proper
procedures to follow when stopping the EMIFA memory controller clocks.
Figure 19-17. EMIFA PSC Block Diagram
19.2.14.1 Power Management Using Self-Refresh Mode
The EMIFA can be placed into a self-refresh state in order to place the attached SDRAM devices into self-
refresh mode, which consumes less power for most SDRAM devices. In this state, the attached SDRAM
device uses an internal clock to perform its own auto refresh cycles. This maintains the validity of the data
in the SDRAM without the need for any external commands. Refer to
for more details on
placing the EMIFA into the self-refresh state.
19.2.14.2 Power Management Using Power Down Mode
In case of power down, to lower the power consumption, EMIFA drives EMA_SDCKE low. EMA_SDCKE
goes high when there is a need to send refresh (REFR) commands, after which EMA_SDCKE is again
driven low. EMA_SDCKE remains low until any request arrives. Refer to
for more details
on placing EMIFA in power down mode.