EMIF
Bits
Value
Description
DDR_A[1]
reg_sdram_drive
SDRAM drive strength from SDRAM Config register
DDR_A[0]
0x1
Disable DLL
•
Starts an auto-refresh cycle in the next cycle.
•
Enters its idle state and can issue any other commands except a write or a read. A write or a read will
only be issued after 1 clock cycles have elapsed since DDR_CKE is driven high. The value
of T_XSRD is taken from SDRAM Timing 2 register.
Exit sequence of self-refresh mode for DDR3 device: The memory controller:
•
Enables clocks.
•
Drives DDR_CKE high.
•
Waits for 1 cycles. The value of T_XSNR is taken from SDRAM Timing 2 register.
•
If the REG_DDR_DISABLE_DLL bit in the SDRAM Config register is 1, issues a LOAD MODE
REGISTER command to the extended mode register 1 with the pad_a_o bits set as follows:
Bits
Value
Description
DDR_A[15:13]
0x0
Reserved
DDR_A[12]
0x0
Output buffer enabled
DDR_A[11]
0x0
TDQS disable
DDR_A[10]
0x0
Reserved
DDR_A[9]
reg_ddr_term[2]
DDR3 termination resistor value from SDRAM Config register
DDR_A[8]
0x0
Reserved
DDR_A[7]
0x0
Write leveling disabled
DDR_A[6]
reg_ddr_term[1]
DDR3 termination resistor value from SDRAM Config register
DDR_A[5]
reg_sdram_drive[1]
SDRAM drive strength from SDRAM Config register
DDR_A[4:3]
0x0
Additive latency = 0
DDR_A[2]
reg_ddr_term[0]
DDR3 termination resistor value from SDRAM Config register
DDR_A[1]
reg_sdram_drive[0]
SDRAM drive strength from SDRAM Config register
DDR_A[0]
0x1
Disable DLL
•
Starts an auto-refresh cycle in the next cycle.
•
Performs one write incremental leveling.
•
Performs read DQS incremental training.
•
Performs read data-eye incremental training.
•
Enters its idle state and can issue any other commands except a write or a read. A write or a read will
only be issued after 1 clock cycles have elapsed since DDR_CKE is driven high. The value
of T_XSRD is taken from SDRAM Timing 2 register.
7.3.3.11.3 Power Down Mode
The memory controller also supports power-down mode for low power. The memory controller
automatically puts the SDRAM into power-sDown after the memory controller is idle for REG_PD_TIM
number of DDR clock cycles and the REG_LP_MODE field is set to 4. The REG_LP_MODE and
REG_PD_TIM fields can be programmed in the Power Management Control register (PMCR). If the
Refresh Must level is not reached before the entry into power-down, the memory controller will not
precharge all banks before issuing the POWER-DOWN command. This will result in SDRAM entering
active power-down mode.
If the Refresh Must level is reached before the entry into power-down, the memory controller will
precharge all banks and issue refreshes until the Refresh Release Level is reached before issuing the
POWER-DOWN command. This will result in SDRAM entering precharge power-down mode.
In power-down mode, the memory controller does not stop the clocks DDR_CLK to the SDRAM. The
memory controller maintains DDR_CKE low to maintain the power-down state.
420
Memory Subsystem
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated