EMIF
When the SDRAM is in power-down, the memory controller services register accesses as normal. If the
REG_LP_MODE field is set not equal to 4, or an SDRAM access is requested, or the Refresh Must level
is reached while the SDRAM is in power-down, the memory controller will bring the SDRAM out of power-
down. For DDR3, memory controller will also exit power-down to perform incremental leveling.
Exit sequence of power-down mode for DDR2, DDR3 and LPDDR1: The memory controller
•
Drives DDR_CKE high after T_CKE + 1 cycles have elapsed since the POWER-DOWN command was
issued. The value of T_CKE is taken from SDRAM Timing 2 register.
•
Waits for T_XP + 1 cycles. The value of T_XP is taken from SDRAM Timing 2 register.
•
Enters its idle state and can issue any commands.
7.3.3.11.4 Deep Power-Down Mode
For ultimate power savings, the memory controller supports deep power-down mode for LPDDR1.
The SDRAM can be forced into deep power-down through software by setting the reg_dpd_en field in the
Power Management Control register to 1. In this case, the memory controller will continue normal
operation until all SDRAM memory access requests have been serviced. At this point the memory
controller will issue a DEEP POWER-DOWN command. The memory controller then maintains pad_cke_o
low to maintain the Deep Power-Down state. In deep power-down mode, the memory controller
automatically stops the clocks to the SDRAM.
Setting the REG_DPD_EN field to 1 overrides the setting of REG_LP_MODE field. Therefore, if the
SDRAM is in Clock Stop, Self Refresh, or Power-Down mode, and REG_DPD_EN field is set to 1, the
memory controller will exit those modes and go into deep power-down mode.
When the SDRAM is in deep power-down, the memory controller services register accesses as normal.
If the REG_DPD_EN field is set to 0, or an SDRAM access is requested, the memory controller will bring
the SDRAM out of deep power-down.
Exit sequence for LPDDR1: The memory controller:
•
Performs SDRAM initialization as specified in the LPDDR1(mDDR) SDRAM Memory Initialization
section.
•
Enters its idle state and can issue any commands.
Since the memory controller performs initialization upon deep power-down exit, the
REG_REFRESH_RATE field in the SDRAM Refresh Control register must be set appropriately to meet
the 200µs wait requirement for LPDDR1.
7.3.3.11.5 Save and Restore Mode
The DDR2/3/mDDR memory controller supports save and restore mechanism to completely switch off
power to the DDR2/3/mDDR memory controller. The following sequence of operations is followed to put
DDR2/3/mDDR memory controller in off mode:
An external master reads the following memory mapped registers and saves their value external to the
DDR2/3/mDDR memory controller.
1. SDRAM Config register (SDRCR)
2. SDRAM Config 2 register
3. SDRAM Refresh Control register (SDRRCR)
4. SDRAM Refresh Control Shadow register (SDRRCSR)
5. SDRAM Timing 1 register (SDRTIM1)
6. SDRAM Timing 1 Shadow register (SDRTIM1SR)
7. SDRAM Timing 2 register (SDRTIM2)
8. SDRAM Timing 2 Shadow register (SDRTIM2SR)
9. SDRAM Timing 3 register (SDRTIM3)
10. SDRAM Timing 3 Shadow register (SDRTIM3SR)
11. Power Management Control register (PMCR)
421
SPRUH73H – October 2011 – Revised April 2013
Memory Subsystem
Copyright © 2011–2013, Texas Instruments Incorporated