1Gb: x4, x8, x16 DDR3 SDRAM
READ Operation
DQS to DQ output timing is shown in Figure 08 (page 166). The DQ transitions between
valid data outputs must be within tDQSQ of the crossing point of DQS, DQS#. DQS must
also maintain a minimum HIGH and LOW time of tQSH and tQSL. Prior to the READ
preamble, the DQ balls will either be floating or terminated, depending on the status of
the ODT signal.
Figure 09 (page 160) shows the strobe-to-clock timing during a READ. The crossing
point DQS, DQS# must transition within ±tDQSCK of the clock crossing point. The data
out has no timing relationship to CK, only to DQS, as shown in Figure 09 (page 160).
Figure 09 (page 160) also shows the READ preamble and postamble. Typically, both
DQS and DQS# are High-Z to save power (VDDQ). Prior to data output from the DRAM,
DQS is driven LOW and DQS# is HIGH for tRPRE. This is known as the READ preamble.
The READ postamble, tRPST, is one half clock from the last DQS, DQS# transition. Dur-
ing the READ postamble, DQS is driven LOW and DQS# is HIGH. When complete, the
DQ is disabled or continues terminating, depending on the state of the ODT signal. on
page demonstrates how to measure tRPST.
PDF: 09005aef826aa906
1Gb_DDR3_SDRAM.pdf - Rev. L 03/13 EN
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