![Texas Instruments AM1808 Скачать руководство пользователя страница 875](http://html.mh-extra.com/html/texas-instruments/am1808/am1808_technical-reference-manual_1094558875.webp)
Architecture
875
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
External Memory Interface A (EMIFA)
19.2.14.3 Power Management Using Clock Stop
The LPSC of the memory controller can be programmed to be in one of the following states:
•
Enable
•
Auto Sleep
•
Auto Wake
•
Sync Reset
After the EMIFA clock is enabled, by default it is in the enable state. EMIFA can be put to auto sleep state,
when the clock is to be gated off. Auto Wake brings back EMIFA to the enable state from the auto sleep
state.
19.2.14.3.1 Auto Sleep and Auto Wake
To achieve maximum power savings EMIFA core clock should be gated off. EMIFA memory controller can
make use of auto sleep and auto wake to achieve clock gating. Following describes the procedure to be
followed to put EMIFA memory controller in auto sleep state:
•
EMIFA should be put to self-refresh mode before stopping the clock. Refer to
for
details on self-refresh mode. The EMIFA memory controller will complete any outstanding accesses
and backlogged refresh cycles and then place the EMIFA memory in self-refresh mode.
•
Then, program the LPSC of EMIFA for auto sleep, to gate off the clocks.
Register and memory access requests are honored while EMIFA is in auto sleep state. When EMIFA sees
a request while it is in auto sleep state, it automatically returns to enable state, processes the request, and
returns back to auto sleep state until further requests come.
On frequent requests, EMIFA switches between auto sleep and enable states. To bring EMIFA back to the
enable state, auto wake can be used. Following procedure is followed for performing auto wake.
•
Program the LPSC of EMIFA for auto wake.
•
Bring EMIFA out of self-refresh. Refer to
for details on self-refresh mode.
After auto wake, EMIFA is in enable state and clocks run continuously.
19.2.14.3.2 Sync Reset and Enable
Sync reset of EMIFA through the LPSC does not reset the EMIFA registers or memory. Thus EMIFA
LPSC sync reset behavior is similar to EMIFA LPSC auto sleep, except that register or memory requests
are not honored by EMIFA. Following is the procedure to put EMIFA in sync reset state:
•
EMIFA should be put to self-refresh mode before stopping the clock. Refer to
for
details on self-refresh mode. The EMIFA memory controller will complete any outstanding accesses
and backlogged refresh cycles and then place the EMIFA memory in self-refresh mode.
•
Then, program the LPSC of EMIFA to Sync-Reset state.
On sync reset, requests to EMIFA are not honored. To bring EMIFA back to the enable state, use the
following enable procedure:
•
Program the LPSC of EMIFA to enter enable state.
•
Bring EMIFA out of self-refresh. Refer to
for details on self-refresh mode.
Now EMIFA memory controller is in the enable state and continues with normal operation.
19.2.15 Emulation Considerations
EMIFA memory controller will remain fully functional during emulation halts, to allow emulation access to
external memory.