Intel
®
81341 and 81342—DDR SDRAM Memory Controller
Intel
®
81341 and 81342 I/O Processors
Developer’s Manual
December 2007
628
Order Number: 315037-002US
7.8.2
SDRAM Control Register 0 — SDCR0
SDRAM Control Registers (SDCR[1:0]) are responsible for programming operation of
the DDR SDRAM state machines. The SDCR0 specifies the DIMM type, data bus width,
and some SDRAM timing parameters required by the DDR SDRAM state machine as
defined in
“DDR SDRAM Initialization” on page 594
and
. The remaining SDRAM timing parameters required by the
DDR SDRAM state machine are set in SDCR1.
Warning:
SPD values read must be converted into MCLK Periods.
Table 375. DDR SDRAM Control Register 0 — SDCR0 (Sheet 1 of 2)
Bit
Default
Description
31:27
00000
2
RAS:
Active to Precharge duration in MCLK periods,
Equation 19.RAS = tRAS - 1
where tRAS is from SPD.
26:24
000
2
RP:
Precharge Command Period in MCLK periods,
Equation 20.RP = tRP - 1
where tRP is from SPD.
23
0
2
Reserved
22:20
000
2
RCD:
Active to Read, Active to Write Period in MCLK periods,
Equation 21.RCD = tRCD - 1
where tRCD is from SPD.
19
0
2
Reserved
18:16
001
2
tEDP:
Data Path Latency in MCLK periods. Recommended tEDP values are provided below.:
Trace Length (Inches) tEDP
8 4H
10 5H
15:14
00
2
Reserved
13:12
00
2
WDL
: Write Latency in MCLK periods:
Equation 22.WDL = tCAS - 2
where tCAS is from SPD.
11
0
2
Reserved
PCI
IOP
Attributes
Attributes
28
24
20
16
12
8
4
0
31
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rv
na
rw
na
rw
na
rw
na
rv
na
rw
na
rw
na
rw
na
rv
na
rv
na
rw
na
rw
na
rv
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rw
na
rv
na
ro
na
rw
na
rw
na
Attribute Legend:
RV = Reserved
PR = Preserved
RS = Read/Set
RW = Read/Write
RC = Read Clear
RO = Read Only
NA = Not Accessible
Intel XScale
®
microarchitecture Local Bus
Address offset
+1804H