Intel
®
81341 and 81342 I/O Processors
December 2007
Developer’s Manual
Order Number: 315037-002US
665
DDR SDRAM Memory Controller—Intel
®
81341 and 81342
7.8.36
DLL Delay for Receive Enable Register — DLLRCVER
This register is used to select the DIMM Type, (i.e., registered versus unbuffered). This
register is also used to position the receive enable signal pulse width relative to the
input data strobes by programming the slave DLL delay values. Note that the receive
enable master delay value is located in the
“DLL Delay Register 4 — DLLR4” on
Note:
The Slave_Delay fields in the register are encoded such that a value of 0 represents 1,
a value of 1 represents 2, and so on.
Note:
When necessary, the user is required to program this register to tune the data strobe
delay and the receive enable delay of the DDR SDRAM Memory Subsystem. However,
after tuning any of the delay values, the Read FIFO must be reset using bit 7 of the
“DDR SDRAM Control Register 0 — SDCR0” on page 628
.
Table 409. DLL Delay for Receive Enable Register — DLLRCVER (Sheet 1 of 3)
Bit
Default
Description
31:25
000000
2
Reserved.
24
0
2
Receive Enable Result bit
: This bit is used by the software algorithm which is used to determine the
optimum receive enable pulse width location. The receive enable pulse width may be shifted relative to
the input data strobes by programming the Receive Enable Slave Delay 1 and Slave Enable Slave Delay
2 fields in this register. When the Receive Enable State Machine is enabled (bit 17) and a DDR memory
location is read, the Receive Enable Result bit indicates the value of the DQS# signals at the rising edge
of the receive enable pulse.
23:19
00000
2
Reserved.
18
1
2
Receive Enable Reset Bit
: This bit is used by the software algorithm which is used to determine the
optimum receive enable pulse width location. The Receive Enable Result bit is cleared by setting the
Receive Enable Reset Bit. The Receive Enable Result bit must be reset through each iteration.
17
0
2
Receive Enable State Machine Enable Bit
: This bit is set to enable the Receive Enable State
Machine. The Receive Enable state machine can be used in conjunction with a software algorithm to
determine the optimum location of the receive enable pulse width relative to the input data strobes. The
receive enable pulse is used to enable the input data strobes only during the time the DDR memory are
driving them in order to avoid erroneous data strobe pulses mainly when the data strobes are floating.
The DDR memory drives pre-amble for about one clock before the first rising edge of the data strobes,
and a post-amble for about a half clock after the data strobes. The goal is to have the receive enable
pulse enables the input data strobes somewhere in the middle of the pre-amble window and disables the
data strobes somewhere in the middle of the post-amble window. The software algorithm can go
through several iterations by gradually increasing the slave delay and verifying the Receive Enable
Result bit to determine the optimum location of the receive enable pulse width.
16
0
2
DIMM Type
: This bit must be programmed based on the DIMM Type being interfaced to the 81341 and
81342DDR Memory Controller. Also refer to bit 0 of the
“DDR SDRAM Control Register 0 — SDCR0” on
.
0 = Registered
1 = Unbuffered
15:11
00000
2
Reserved.
PCI
IOP
Attributes
Attributes
28
24
20
16
12
8
4
0
31
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
rv
na
ro
na
rv
na
rv
na
rv
na
rv
na
rv
na
rw
na
rw
na
rw
na
rv
na
rv
na
rv
na
rv
na
rv
na
rw
na
rw
na
rw
na
rv
na
rv
na
rv
na
rw
na
rw
na
rw
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 offset
+2030H