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Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
August 2006
Developer’s Manual
Order Number: 306262-004US
635
Memory Controller—Intel
®
IXP45X and Intel
®
IXP46X Product Line of Network Processors
11.6.3
DDRI SDRAM Control Register 1 SDCR1
The SDRAM Control Registers (SDCR[1:0]) are responsible for programming the
operation of the DDRI SDRAM state machines as defined in
SDRAM Initialization” on page 598
and
Section 11.2.2.9, “DDRI SDRAM Mode
. The SDCR1 specifies the remaining SDRAM timing
parameters required by the DDRI SDRAM state machine not specified in SDCR0.
Note:
Each parameter field contains either an IXP45X/IXP46X network processors-required
value limit or an example value derived from a typical device datasheet.
Register Name:
DDRI SDRAM Control Register 1 - SDCR1
Hex Offset Address:
CC00 E508H
Reset Hex Value:
0x0000 0000H
Register Description:
DDRI SDRAM Control Register 1
Access: See below.
31 30
28 27
24 23 22
20 19
17 16
12 11
09 08
04 03 02
00
(Rsvd
)
(Rsvd
)
(Rsvd)
R
Register
DDRI SDRAM Control Register 1 - SDCR1 (External Version) (Sheet 1 of 2)
Bits
Name
Description
Default
Access
31
(Reserved)
RESERVED for DDRII. A value of 0
2
must be used for the IXP45X/
IXP46X network processors.
0
2
RW
30:2
8
RTCMD
RTCMD: Read to non-Write Command turnaround period in MCLK
periods. A value of 010
2
must be programmed for the IXP45X/IXP46X
network processors.
000
2
RW
27:2
4
WTCMD
WTCMD: Write to Command (non-Read) turnaround period in MCLK
periods. This value is computed by using the CAS Latency (t
CAS
)and
Write Recovery (t
WR
) measured for the device (provided in the JEDEC/
Vendor specification) using the following equation:
Equation 6. WTCMD = t
CAS
+ t
WR
NOTE: t
CAS
and t
WR
must be converted to mclks for this equation.
For example, a device specification yields that t
CAS
is 2.5 mclks and
t
WR
is 15ns (and the device speed is 133MHz, so the mclk period is
7.5ns).
t
WR
= (15ns / 7.5ns) = 2 mclks.
Thus, WTCMD = 2.5 + 2 = 4.5, round up to 5 mclks, so a value of
0101
2
should be programmed.
000
2
RW
23
(Reserved)
0
2
RO