EMIF
The DDR2/3/mDDR memory controller does not perform full leveling after initialization upon reset
deassertion. Full leveling must be triggered by software after the DDR2/3/mDDR memory controller
registers are properly configured. The DDR2/3/mDDR memory controller supports triggering of full leveling
through software through the use of the REG_RDWRLVLFULL_START field in the Read-Write Leveling
Control register(RWLCR). Since full leveling takes considerable amount of time and refreshes cannot be
issued to DDR3 when DDR3 is put in leveling mode, refresh interval will be violated and data inside DDR3
can be lost. Although, this is not an issue at power-up, this might be an issue if full leveling is triggered
when DDR3 is functional.
The memory controller supports incremental leveling to better track voltage and temperature changes
during normal operation. The incremental leveling can be enabled by writing a non-zero value to the
REG_WRLVLINC_INT, REG_RDLVLGATEINC_INT, and REG_RDLVLINC_INT fields in the Read-Write
Leveling Control register(RWLCR). The memory controller periodically triggers incremental write leveling
every time REG_WRLVLINC_INT expires. In other words, the REG_WRLVLINC_INT defines the interval
between successive incremental write leveling.
Similarly, the memory controller periodically triggers incremental read DQS gate training every time
REG_RDLVLGATEINC_INT expires, and triggers incremental read data eye training every time
REG_RDLVLINC_INT expires.
To minimize impact on bandwidth, the software can program these intervals such that these three
intervals do not expire at same time. The value of interval programmed is dependent on the slope of
voltage and temperature changes.
The memory controller supports increasing the rate of incremental leveling automatically for a defined
period of time. This can be achieved by programming the Read-Write Leveling Ramp Window
register(RDWR_LVL_RMP_WIN) and the Read-Write Leveling Ramp Control
register(RDWR_LVL_RMP_CTRL). Whenever a pulse is received, the memory controller would use the
intervals programmed in the Read-Write Leveling Ramp Control register until the
REG_RDWRLVLINC_RMP_WIN in the Read-Write Leveling Ramp Window register expires. After the
expiration of REG_RDWRLVLINC_RMP_WIN the memory controller switches back to use the intervals
programmed in the Read-Write Leveling Control register.
To guarantee none of the incremental leveling events are missed, the REG_RDWRLVLINC_RMP_WIN
must be programmed greater than the intervals in the Read-Write Leveling Ramp Control register.
If the memory controller is in Self-Refresh or Power-Down modes when any of the incremental leveling
intervals expire, the memory controller will exit Self-Refresh or Power-Down mode, perform the required
leveling, and then re-enter the Self-Refresh or Power-Down mode. The memory controller also triggers
incremental leveling on Self-Refresh exit.
7.3.3.7
PRCM Sequence for DDR2/3/mDDR Memory controller
The memory controller clock, reset and power are handled by the device PRCM module. Refer to the
Power Reset Clock Management (PRCM) chapter for the PRCM register details.
7.3.3.8
Interrupt Support
The DDR2/3/mDDR controller is compliant with Open Core Protocol Specification (OCP-IP 2.2). The
controller supports only Idle, Write, Read, and WriteNonPost command types. Also, the controller supports
only incrementing, wrapping, and 2-dimensional block addressing modes. The controller supports
generation of an error interrupt if an unsupported command or a command with unsupported addressing
mode is received.
7.3.3.9
EDMA Event Support
The DDR2/3/mDDR memory controller is a DMA slave peripheral and therefore does not generate EDMA
events. Data read and write requests may be made directly by masters including the EDMA controller.
7.3.3.10 Emulation Considerations
The DDR2/3/mDDR memory controller will remain fully functional during emulation halts to allow emulation
access to external memory.
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Memory Subsystem
SPRUH73H – October 2011 – Revised April 2013
Copyright © 2011–2013, Texas Instruments Incorporated