DDR3 SDRAM in Stratix III Devices Design Flow
Page 29
© November 2008
Altera Corporation
AN 436: Using DDR3 SDRAM in Stratix III and Stratix IV Devices
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Write leveling t
DQSS
setup and hold margin
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Write leveling t
DSS
and t
DSH
setup and hold margin
f
For detailed information about timing analysis and reporting using the
ALTMEMPHY megafunction, refer to
AN 438: Constraining and Analyzing Timing for
Adjust Constraints
In the timing report of the design, you can see the worst case setup and hold margin
for the different paths in the design. If the setup and hold margin are unbalanced,
achieve a balanced setup and hold margin by adjusting the phase setting of the clocks
that clock these paths.
For example, for the address and command margin, the address and command
outputs are clocked by an address and command clock that can be different with
respect to the system clock, which is 0°. The system clock clocks the clock outputs
going to the memory. If the report timing script indicates that using the default phase
setting for the address and command clock results in more hold time than setup time,
adjust the address and command clock to be less negative than the default phase
setting with respect to the system clock so that there is less hold margin. Similarly,
adjust the address and command clock to be more negative than the default phase
setting with respect to the system clock if there is more setup margin.
f
For detailed information about the clocks that the ALTMEMPHY megafunction uses,
refer to the
ALTMEMPHY Megafunction User Guide
Determine Board Design Constraints and Perform Board-Level Simulations
To determine the correct board constraints, run board-level simulations to see if the
settings provide the optimal signal quality. With many variables that can affect the
signal integrity of the memory interface, simulating the memory interface provides an
initial indication of how well the memory interface performs. There are various
electronic design automation (EDA) simulation tools available to perform board-level
simulations. The simulations should be performed on the data, data strobe, control,
command, and address signals. If the memory interface does not have good signal
integrity, adjust the settings, such as drive strength setting, termination scheme or
termination values to improve the signal integrity (realize that changing these settings
affects the timing and it may be necessary to go back to the timing closure if these
change).
f
For detailed information about understanding the different effects on signal integrity
design, refer to
AN 520: DDR3 SDRAM Interface Termination and Layout Guidelines
.
Trace information from your board-level simulation should be fed back into the
Quartus II advanced I/O timing information.