Altera DDR SDRAM High-Performance Controllers and ALTMEMP Manual de usuario Pagina 70

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5–24 Chapter 5: Functional Description—ALTMEMPHY
Block Description
External Memory Interface Handbook Volume 3 June 2011 Altera Corporation
Section I. DDR and DDR2 SDRAM Controllers with ALTMEMPHY IP User Guide
Stratix III and Stratix IV Devices
Stratix IV and Stratix III devices support half-rate or full-rate DDR/DDR2 SDRAM.
The Stratix IV and Stratix III read datapath (Figure 5–8) consists of two main blocks:
Data capture, resynchronization, and demultiplexing
Read datapath logic (read datapath)
Data Capture, Resynchronization, and Demultiplexing
In Stratix IV and Stratix III devices, the smart interface module in the IOE performs
the following tasks:
Captures the data
Resynchronizes the captured data from the DQS domain to the resynchronization
clock (
resync_clk_1x
) domain
Converts the resynchronized data into half-rate data, which is performed by
feeding the resynchronized data into the HDR conversion block within the IOE,
which is clocked by the half-rate version of the resynchronization clock. The
resync_clk_1x
signal is generated from the I/O clock divider module based on
the
resync_clk_2x
signal from the PLL.
f For more information about IOE registers, refer to the External Memory Interfaces in
Stratix III Devices chapter in volume 1 of the Stratix III Device Handbook and the
External Memory Interfaces in Stratix IV Devices chapter in volume 1 of the Stratix IV
Device Handbook.
Figure 5–8. DDR/DDR2 SDRAM Data Capture and Read Data Mapping in Stratix IV and Stratix III Devices
Note to Figure 5–8:
(1) This figure shows a half-rate variation. For a full-rate controller,
dio_radata2_1x
and
dio_rdata3_1x
are unconnected.
Dual Port RAM
Read Datapath
Data Capture, Resynchronization,
and Data Demultiplexing
mem_dq
dio_rdata3_1x
IOE
mem_dqs
mem_dqsn
dio_rdata2_1x
dio_rdata1_1x
dio_rdata0_1x
resync_clk_1x
4n bits
wr_data
wr_clk
rd_data
rd_clk
ctl_rdata
ram_rdata_1x[4n]
phy_clk_1x
Data
Mapping
Logic
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