Texas Instruments TMS320C6455 manual Sdram Configuration Register Sdcfg

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4.3SDRAM Configuration Register (SDCFG)

The SDRAM configuration register (SDCFG) contains fields that program the DDR2 memory controller to meet the specification of the DDR2 memory. These fields configure the DDR2 memory controller to match the data bus width, CAS latency, number of internal banks, and page size of the external DDR2 memory. Bits 0-14 of the SDCFG register are only writeable when the TIMUNLOCK bit is set to 0 (unlocked). for more information on initializing the configuration registers of the DDR2 memory controller, see

Section 2.11.1. The SDCFG register is shown in Figure 21 and described in Table 20.

Figure 21. SDRAM Configuration Register (SDCFG)

31								24
				Reserved
				R-0x0
23	22			19		18	17	16
BOOT_		Reserved				DDR_DRIVE	Reserved
UNLOCK
R/W-0		R/W-0xA				R-0		R-0x3
15	14	13	12	11			9	8
TIMUNLOCK	NM	Reserved				CL			Reserved
R/W-0	R/W-0	R-0x0				R/W-0x5			R-0x0
7	6		4	3		2		0
Reserved		IBANK			Reserved		PAGESIZE
R-0x0		R/W-0x2			R-0x0		R/W-0x0

LEGEND: R/W = Read/Write; R = Read only; -n= value after reset

Table 20. SDRAM Configuration Register (SDCFG) Field Descriptions

Bit	Field	Value	Description
31-24	Reserved		Reserved. Writes to this register must keep these bits at their default values.
23	BOOT_UNLOCK		Boot unlock bit. Controls write access to bits 16-22 and 27 of this register.
		0	Writes to bits 22:16 of this register are not permitted.
		1	Writes to bits 22:16 of this register are allowed.
22-19	Reserved		Reserved. Writes to this register must keep these bits at their default value.
18	DDR_DRIVE		DDR2 SDRAM drive strength. This bit is used to select the drive strength used by the DDR2
			SDRAM. This bit is writeable only when BOOT_UNLOCK is unlocked (set to 1).
		0	Normal drive strength.
		1	Weak (60%) drive strength.
17-16	Reserved		Reserved. Writes to this register must keep these bits at their default value.
15	TIMUNLOCK		Timing unlock bit. Controls write access for the SDRAM Timing Register (SDTIM1) and
			SDRAM Timing Register 2 (SDTIM2). A write to this bit causes the DDR2 Memory Controller
			to start the SDRAM initialization sequence.
		0	Register fields in the SDTIM1 and SDTIM2 registers may not be changed.
		1	Register fields in the SDTIM1 and SDTIM2 registers may be changed.
14	NM		DDR2 data bus width. A write to this bit will cause the DDR2 Memory Controller to start the
			SDRAM initialization sequence.
		0	32-bit bus width.
		1	16-bit bus width
13-12	Reserved		Reserved. The reserved bit location is always read as 0. A value written to this field has no
			effect.

SPRU970G – December 2005 – Revised June 2011	C6455/C6454 DDR2 Memory Controller	41
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