
DDR2 memory controller data bus
DDR_D[15:8]
DDR_D[7:0]
16-bit memory device
DDR_CLK
DDR_CKE
DDR_CS
DDR_RAS
DDR_WE
DDR_BA[2:0]
COL
MRS/EMRS
DDR_A[13:0]
DDR_CAS
BANK
DDR_CLK
Architecture
380
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
14.2.3.6 Mode Register Set (MRS and EMRS)
DDR2/mDDR SDRAM contains mode and extended mode registers that configure the DDR2/mDDR
memory for operation. These registers control burst type, burst length, CAS latency, DLL enable/disable
(on DDR2/mDDR device), single-ended strobe, differential strobe etc.
The DDR2/mDDR memory controller programs the mode and extended mode registers of the
DDR2/mDDR memory by issuing MRS and EMRS commands. When the MRS or EMRS command is
executed, the value on DDR_BA[2:0] selects the mode register to be written and the data on DDR_A[13:0]
is loaded into the register.
shows the timing for an MRS and EMRS command.
The DDR2/mDDR memory controller only issues MRS and EMRS commands during the DDR2/mDDR
memory controller initialization sequence. See
for more information.
Figure 14-10. DDR2/mDDR MRS and EMRS Command
14.2.4 Memory Width and Byte Alignment
The DDR2/mDDR memory controller supports memory widths of 16 bits.
summarizes the
addressable memory ranges on the DDR2/mDDR memory controller. Only little-endian format is
supported.
shows the byte lanes used on the DDR2/mDDR memory controller. The external
memory is always right aligned on the data bus.
Table 14-3. Addressable Memory Ranges
Memory Width
Maximum addressable bytes per CS space
Description
×16
256 Mbytes
Halfword address
Figure 14-11. Byte Alignment