Altera DDR SDRAM High-Performance Controllers and ALTMEMP Instrukcja Użytkownika Strona 82

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5–36 Chapter 5: Functional Description—ALTMEMPHY
PHY-to-Controller Interfaces
External Memory Interface Handbook Volume 3 June 2011 Altera Corporation
Section I. DDR and DDR2 SDRAM Controllers with ALTMEMPHY IP User Guide
For half-rate designs, the AFI allows the controller to issue reads and writes that are
aligned to either half-cycle of the half-rate
phy_clk
, which means that the datapaths
can support multiple data alignments—word-unaligned and word-aligned writes and
reads. Figure 5–12 and Figure 5–13 display the half-rate write operation.
Figure 5–14 shows a full-rate write.
After calibration completes, the sequencer sends the write latency in number of clock
cycles to the controller.
Figure 5–12. Half-Rate Write with Word-Unaligned Data
Figure 5–13. Half-Rate Write with Word-Aligned Data
Figure 5–14. Full-Rate Write
00 11 0001
00
11
0110 00
-- a x cb xd
ctl_clk
ctl_dqs_burst
ctl_wdata_valid
ctl_wdata
00
10
11
00
00
11
00
-- ba --dc
ctl_clk
ctl_dqs_burst
ctl_wdata_valid
ctl_wdata
-- a --b
ctl_clk
ctl_dqs_burst
ctl_wdata_valid
ctl_wdata
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