Texas Instruments TMS320DM643 manual DDR VTP Register Ddrvtpr, DDR VTP Enable Register Ddrvtper

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DDR2 Memory Controller Registers

4.13 DDR VTP Register (DDRVTPR)

The DDR VTP register (DDRVTPR) is used in conjunction with the VTP IO control register (VTPIOCR) to calibrate the output impedance of the DDR2 memory controller IOs with respect to voltage, temperature, and process. Following the calibration sequence, DDRVTPR contains the information needed to calibrate the impedance of the IO. Once the calibration sequence has completed, DDRVTPR should be read and the data written to the PCH and NCH fields in VTPIOCR. The DDRVTPR is shown in Figure 31 and described in Table 37.

Figure 31. DDR VTP Register (DDRVTPR)

31					16
		Reserved
		R-0
15	10	9	5	4	0
Reserved		PCH			NCH
R-0		R-0			R/W-0

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

			Table 37. DDR VTP Register (DDRVTPR) Field Descriptions
Bit	Field	Value	Description
31-10	Reserved	0	Reserved.
9-5	PCH	0-1Fh	P channel value for IO impedance calibration. Following the VTP calibration sequence, this value should
			be read and written to the PCH field in the VTP IO control register (VTPIOCR).
4-0	NCH	0-1Fh	N channel value for IO impedance calibration. Following the VTP calibration sequence, this value
			should be read and written to the NCH field in the VTP IO control register (VTPIOCR).

4.14 DDR VTP Enable Register (DDRVTPER)

The DDR VTP enable register (DDRVTPER) is used to enable/disable accesses to the DDR VTP register (DDRVTPR). Writing a value of 1 to DDRVTPER enables accesses to DDRVTPR and writing a value of 0 disables accesses to DDRVTPR. The DDRVTPER is shown in Figure 32 and described in Table 38.

Figure 32. DDR VTP Enable Register (DDRVTPER)

31		16
Reserved
R-0
15	1	0
Reserved		EN
R-0		R/W-0

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

Table 38. DDR VTP Enable Register (DDRVTPER) Field Descriptions

Bit	Field	Value	Description
31-1	Reserved	0	Reserved. Always write 0 to these bits.
0	EN		DDRVTPR access enable.
		0	Access to DDRVTPR is disabled.
		1	Access to DDRVTPR is enabled.

54	DDR2 Memory Controller	SPRU986B–November 2007
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