Architecture
393
SPRUH82C – April 2013 – Revised September 2016
Copyright © 2013–2016, Texas Instruments Incorporated
DDR2/mDDR Memory Controller
Table 14-11. DDR2 SDRAM Configuration by MRS Command
Memory
Controller
Address Bus
Value
DDR2/mDDR
SDRAM
Register Bit
DDR2/mDDR
SDRAM Field
Function Selection
DDR_A[12]
0
12
Power Down Exit
Fast exit
DDR_A[11:9]
t_WR
11:9
Write Recovery
Write recovery from autoprecharge. Value of 2,
3, 4, 5, or 6 is programmed based on value of
the T_WR bit in the SDRAM timing register 1
(SDTIMR1 ).
DDR_A[8]
0
8
DLL Reset
Out of reset
DDR_A[7]
0
7
Mode: Test or Normal
Normal mode
DDR_A[6:4]
CL bit
6:4
CAS Latency
Value of 2, 3, 4, or 5 is programmed based on
value of the CL bit in the SDRAM configuration
register (SDCR).
DDR_A[3]
0
3
Burst Type
Sequential
DDR_A[2:0]
3h
2:0
Burst Length
Value of 8
Table 14-12. DDR2 SDRAM Configuration by EMRS(1) Command
Memory
Controller
Address Bus
Value
DDR2/mDDR
SDRAM
Register Bit
DDR2/mDDR
SDRAM Field
Function Selection
DDR_A[12]
0
12
Output Buffer Enable
Output buffer enable
DDR_A[11]
0
11
RDQS Enable
RDQS disable
DDR_A[10]
1
10
DQS enable
Disables differential DQS signaling.
DDR_A[9:7]
0
9:7
OCD Calibration Program
Exit OCD calibration
DDR_A[6]
0
6
ODT Value (Rtt)
Cleared to 0 to select 75 ohms. This feature
is not supported because the DDR_ODT
signal is not pinned out.
DDR_A[5:3]
0
5:3
Additive Latency
0 cycles of additive latency
DDR_A[2]
1
2
ODT Value (Rtt)
Set to 1 to select 75 ohms. This feature is not
supported because the DDR_ODT signal is
not pinned out.
DDR_A[1]
DDRDRIVE[0]
1
Output Driver Impedance
Value of 0 or 1 is programmed based on
value of DDRDRIVE0 bit in SDRAM
configuration register (SDCR).
DDR_A[0]
0
0
DLL enable
DLL enable
Table 14-13. Mobile DDR SDRAM Configuration by MRS Command
Memory
Controller
Address Bus
Value
mDDR SDRAM
Register Bit
mDDR SDRAM Field
Function Selection
DDR_A[11:7]
0
11:7
Operating mode
Normal operating mode
DDR_A[6:4]
CL bit
6:4
CAS Latency
Value of 2 or 3 is programmed based on
value of CL bit in SDRAM configuration
register (SDCR).
DDR_A[3]
0
3
Burst Type
Sequential
DDR_A[2:0]
3h
2:0
Burst Length
Value of 8