Texas Instruments TMS320DM643 manual DDR2 SDRAM Configuration by MRS Command

www.ti.com

Peripheral Architecture

Table 14. DDR2 SDRAM Configuration by MRS Command

DDR2 Memory
Controller		DDR2 SDRAM
Address Bus	Value	Register Bit	DDR2 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
				(SDTIMR).
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 bank
				configuration register (SDBCR).
DDR_A[3]	0	3	Burst Type	Sequential
DDR_A[2:0]	3h	2:0	Burst Length	8

Table 15. DDR2 SDRAM Configuration by EMRS(1) Command

DDR2 Memory
Controller		DDR2 SDRAM
Address Bus	Value	Register Bit	DDR2 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]	1	1	Output Driver Impedance	DDR2 drive strength programmed to weak
				(60%).
DDR_A[0]	0	0	DLL enable	DLL enable

2.13.1Initializing Configuration Registers

Perform the following steps when configuring the DDR2 memory controller memory-mapped registers:

1.Program the DDR PHY control register (DDRPHYCR) by setting the read latency (READLAT) bits to the desired value as well as clearing the DLLPWRDN bit to 0.

2.Program the SDRAM bank configuration register (SDBCR) to the desired value with the TIMUNLOCK bit set to 1 (unlocked).

3.Program the SDRAM timing register (SDTIMR) and SDRAM timing register 2 (SDTIMR2) to the desired values to meet the DDR2 SDRAM memory data sheet specification.

4.Program SDBCR to the desired value with the TIMUNLOCK bit cleared to 0 (locked).

5.Program the RR bit in the SDRAM refresh control register (SDRCR) to the desired value to meet the refresh requirements of the DDR2 SDRAM memory.

32 DDR2 Memory Controller SPRU986B–November 2007

Submit Documentation Feedback