440EP – PPC440EP Embedded Processor
Revision 1.26 – April 25, 2007
Data Sheet
DDR1 SDRAM I/O Specifications
The DDR1 SDRAM controller times its operation with internal PLB clock signals and generates MemClkOut0 from
the PLB clock. The PLB clock is an internal signal that cannot be directly observed. However MemClkOut0 is the
same frequency as the PLB clock signal and is in phase with the PLB clock signal.
Note:
MemClkOut0 can be advanced with respect to the PLB clock by means of the SDRAM0_CLKTR
programming register. In a typical system, users advance MemClkOut by 90°. This depends on the specific
application and requires a thorough understanding of the memory system in general (refer to the DDR
SDRAM controller chapter in the
PowerPC 440EP User’s Manual).
In the following sections, the label MemClkOut0(0) refers to MemClkOut0 when it has not been phase-shifted, and
MemClkOut0(90) refers to MemClkOut0 when it has been phase-advanced 90°. Advancing MemClkOut0 by 90°
creates a 3/4 cycle setup time and 1/4 cycle hold time for the address and control signals in relation to
MemClkOut0(90). The rising edge of MemClkOut0(90) aligns with the first rising edge of the DQS signal.
The following DDR data is generated by means of simulation and includes logic, driver, package RLC, and lengths.
Values are calculated over best case and worst case processes with speed, temperature, and voltage as follows:
Best Case = Fast process, -40°C, +1.6V
Worst Case = Slow process, +85°C, +1.4V
Note:
In all the following DDR tables and timing diagrams,
minimum
values are measured under
best
case
conditions and
maximum
values are measured under
worst
case conditions.
The signals are terminated as indicated in the figure below for the DDR timing data in the following sections.
Figure 7. DDR SDRAM Simulation Signal Termination Model
MemClkOut0
10pF
120Ω
10pF
MemClkOut0
V
TT
= SV
DD
/2
PPC440EP
50Ω
Addr/Ctrl/Data/DQS
30pF
Note:
This diagram illustrates the model of the DDR SDRAM interface used when generating simulation timing data.
It is
not
a recommended physical circuit design for this interface. An actual interface design will depend on many
factors, including the type of memory used and the board layout.
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