ECP5 and ECP5-5G High-Speed I/O Interface
Technical Note
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FPGA-TN-02035-1.3
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.
5.10.
GDDRX2_TX.ECLK.Centered
This interface is used to implement Generic Transmit DDR with 2x gearing using Edge Clock (ECLK). The clock output is
centered to the data output.
This DDR interface uses the following modules:
ODDRX2F for X2 gearing 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 CLKDIVF module.
The same ECLK and SCLK are used for both data and clock generation.
The EHXPLLL element is used to generate the clocks for the data and clock ODDR modules. The clock used to
generate the clock output is delayed 90 to center to data at the output.
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.
Optionally, you can choose to use the DELAYG or DELAYF element to delay the data output.
The output data can be optionally tristated using either a Tristate input going through an I/O register.
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.
D[3:0]
SCLK
RST
Q
Data [3/7/9:0]
SCLK
RST
Q
“0101”
Refclk
Dout
Clkout
ECLK
CLKDIVF
CLKI
RST
ALIGNWD
CDIVX
D[3:0]
ECLK
ODDRX2F
Edge 1
Primary
Sclk
EHXPLLL
CLKOP
CLKI
RST
CLKOS
LOCK
1'b 0
Edge 2
ECLKI
STOP
ECLKO
ECLKSYNCB
Reset
GDDR_SYNC
Sync _clk
RST
START
SYNC_CLK
DDR_RESET
STOP
READY
Pll _reset
Ready
ODDRX2F
Figure 5.14. GDDRX2_TX.ECLK.Centered 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.