ECP5 and ECP5-5G High-Speed I/O Interface
Technical Note
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FPGA-TN-02035-1.3
25
5.11.
GDDRX71_TX.ECLK
This interface is used to implement transmit side of the 7:1 LVDS interface DDR using the 7 to 1 gearing with ECLK. The
clock output is aligned to the data output.
This DDR interface uses the following modules:
ODDRX71B is used to generate the data output.
The high-speed ECLK is routed to the Edge Clock tree through the ECLKSYNCB module.
The SCLK is routed on the primary clock tree and is generated from the ECLK using the CLKDIVD module.
The same ECLK and SCLK are used for both data and clock generation.
The startup synchronization soft IP (GDDRX_SYNC) is required for this interface to tolerate the skew between the
ECLKSYNCB Stop input and the Reset to the DDR and CLKDIV modules.
The ECLKBRIDGE can be optionally enabled if the data bus is crossing over between the left and right sides of the
device. If ECLKBRIDGE is enabled, then the ECLKBRIDGECS element should be used in the interface before the
ECLKSYNCB element. This element can be enabled through Clarity Designer.
SCLK
RST
Q
ODDRX71B
Data0 [6:0]
SCLK
RST
Q
7'b1100011
Dout
Clkout
ECLK
ECLKI
STOP
ECLKO
CLKDIVF
CLKI
RST
ALIGNWD
CDIVX
D [6:0]
ECLK
(divby 3.5)
Edge
Primary
Sclk
Refclk
D [6:0]
ECLKSYNCB
“0”
sync_reset
GDDR_SYNC
Sync _clk
Start
RST
START
SYNC_CLK
DDR_RESET
STOP
READY
Ready
ODDRX71B
Figure 5.15. GDDRX71_TX.ECLK Interface
Interface Requirements
The SCLK input to the output DDR modules must be routed on the primary clock tree and the ECLK input is routed
on the Edge Clock tree.
USE PRIMARY preference may be assigned to the SCLK net.
You must set the timing preferences as indicated in the
Timing Analysis for High Speed DDR Interfaces
section.
5.12.
Generic DDR Design Guidelines
This section describes the various design guidelines used for building generic high-speed DDR interfaces in ECP5 and
ECP5-5G devices. In additional to these guidelines, it is also required to follow the Interface Rules described for each
type of interface, you need to find the interface you are building in the
High-Speed DDR Interface Details
5.12.1.
Using the High Speed Edge Clock Bridge
The High Speed Edge Clock Bridge is available to wide data busses to bridge the Edge Clock from one side to the other.
To enable this bridge, instantiate the ECLKBRIDGECS element in the HDL design. When using the ECLKBRIDGE, both the
ECLK1 or ECLK0 on that side (spanning both the banks are used). This reduces the number of interfaces that can be
built on a given side. See
ECP5 and ECP5-5G sysClock PLL/DLL Design and Usage Guide (FPGA-TN-02200)
details.