Zynq-7000 AP SoC and 7 Series FPGAs MIS v4.1
147
UG586 November 30, 2016
Chapter 1:
DDR3 and DDR2 SDRAM Memory Interface Solution
The timing diagram for write leveling is shown in
. Periodic
DQS
pulses are
output by the FPGA memory interface to detect the level of the
CK
clock at the DDR3
SDRAM device. The interval between
DQS
pulses is specified as a minimum of 16 clock
cycles.
DQS
is delayed using the PHASER_OUT fine and coarse delay in unit tap increments
until a
0
to
1
transition is detected on the feedback
DQ
input. The
DQS
delay established by
write leveling ensures the
t
DQSS
specification.
shows that the worst-case delay required during write leveling can be one tCK
(DDR3 SDRAM clock period).
X-Ref Target - Figure 1-62
Figure 1-62:
Write Leveling Block Diagram
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X-Ref Target - Figure 1-63
Figure 1-63:
Write Leveling Timing Diagram
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