DDR Interface
Figure 3-1. Nominal Turnaround Time Timing Diagram
Clock
Postamble
A
Preamble A
Preamble B
DQS
Data
B-0
Data
B-3
Data
A-0
Data
A-1
Data
A-2
Data
A-3
Data
B-1
Data
B-2
DQ
Read to Read turnaround (nominal)
Clock
DQS
DQ
Preamble R
(read)
Postamble
R
Preamble W
(write)
Data
W-0
Data
W-3
Data
R-0
Data
R-1
Data
R-2
Data
R-3
Data
W-1
Data
W-2
Read to Write turnaround (nominal)
Clock
DQS
DQ
Postamble Preamble R
Preamble W
(write)
Postamble
R
W
(read)
Data
W-0
Data
W-3
Data
W-1
Data
W-2
Data
R-0
Data
R-1
Data
R-2
Data
R-3
Write to Read turnaround (nominal)
3.7
S3 State Background Description
S3 is a platform power down state where DRAM memory contents are preserved while
the rest of the platform powers down. This state is described more formally in the
Advanced Configuration and Power Interface Specification. It is much like the Standby
mode on mobile computers.
Functionally, the requirement for an AMB is that after a sequence in which:
• AMBS3 Recovery state is stored by the host,
• DRAMs are put into Self-Refresh,
• RESET# is asserted,
• Vcc (1.5 V), Vtt (0.9 V) and VddSPD(3.3 V) are powered down,
The contents of memory on the DIMM are preserved until S3 Recovery. Recovery
requires that the memory on the DIMM be restored without losing data integrity.
The recovery sequence is much the same as an initial power on with the exceptions of:
• Vdd is already powered on
• DDR interface state is restored from stored register values (since no calibration
which might compromise memory content is allowed)
To minimize DIMM current, VCC should be powered up during VTT transitions. The AMB
determines that it is in the S3 mode by checking that VDD (1.8 V) is powered up and
that VCC (1.5 V) is powered off. When in S3 the AMB drives all command/address
outputs (including CKE, ODT, and CLK) to a low. This keeps the DRAM in auto-refresh
and helps prevent DRAM data corruption. When coming out of the S3 mode, if the
system brings VTT (0.9 V) up before VCC the AMB will drive low into the VTT pull-up
circuitry. This causes significant current (approximately two times average but still
normal) to flow from VTT into the AMB until VCC is powered up and the AMB comes out
of S3.
Intel® 6400/6402 Advanced Memory Buffer Datasheet
31
INTEL [ INTEL ]
