DDR2 Memory Controller User's Guide

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4.11 DDR PHY Control Register (DDRPHYCR)
DDR2 Memory Controller Registers
The DDR PHY control register (DDRPHYCR) configures the DDR2 memory controller DLL for operation
and determines whether the DLL is in reset, whether it is powered up, and the read latency. The
DDRPHYCR is shown in Figure 29 and described in Table 35 .
Figure 29. DDR PHY Control Register (DDRPHYCR)
31 16
Reserved
R/W-5000h
15 6 5 4 3 2 0
Reserved DLLRESET DLLPWRDN Rsvd READLAT
R/W-190h R/W-0 R/W-1 R-1 R/W-7h
LEGEND: R/W = Read/Write; R = Read only; - n = value after reset
Table 35. DDR PHY Control Register (DDRPHYCR) Field Descriptions
Bit Field Value Description
31-16 Reserved 5000h Reserved. Always write 5000h to these bits.
15-6 Reserved 190h Reserved. Always write 190h to these bits.
5 DLLRESET Reset DLL.
0 DLL is out of reset.
1 Places the DLL in reset.
4 DLLPWRDN Power down DLL.
0 DLL is powered up.
1 DLL is powered down, if DLLPWRDN and the SR bit and MCLKSTOPEN bit in the SDRAM
refresh control register (SDRCR) are set to 1.
3 Reserved 1 Reserved
2-0 READLAT 0-7h Read latency. Read latency is equal to CAS latency plus round trip board delay for data
minus 1. The maximum value of read latency that is supported is CAS latency plus 3. The
minimum read latency value that is supported is CAS latency plus 1. The read latency value
is defined in number of MCLK/DDR_CLK cycles.
52 DDR2 Memory Controller SPRU986B – November 2007
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